My old notes for this are long gone, but I remember some unpublished updates to my old spell advice. Let's see what I can scrounge. If I omitted a spell that's on the list, I don't have any comment. If I struck a spell, it's because I think it should be removed, with reasons in italics. The rest of the entries are rewrites (either for grammar or rethinking) or new spells.
I looked at the Heart spells from CM, but only Heart of Water with its swift Freedom of Movement a level early on top of an already-spiffy spell effect is worth casting. The others are meh.
Can we lose the spoiler tags? They don't play nicely with the PSP web browser.
[spoiler]0th Level
Guidance: Tell your Rogue to ask for "guidance" prior to every trap he attempts to disarms or UMD roll he has to make (outside of combat). That +1 bonus can be critical. This doesn't stack with Inspire Competence or pretty much any skill-boosting magic item, however.
Light: Remember, you lose darkvision when you Wild Shape, even if your chosen form or your natural race in humanoid form has it. (Obviously, this doesn't apply to situations where you're getting Ex special qualities of your form, as with Exalted or Dragon Wild Shape.)
1st Level
Aquatic EscapeCSc: Change into a fish for 1 round/level. Good for sudden escapes or quick responses to getting dumped into water. This spell just plain sucks, even before you get Wild Shape. Less than 30 seconds of swimming/water breathing is not going to save you, and even if it would, you can't cast this spell because it has a verbal component!
Babau SlimeSC: Great for grappling druids, and a general-purpose damage buff for any Wild Shaping Druid. The shortish duration and relatively low damage, along with the situational inconvenience of being covered with acid, makes this a rather poor spell. It doesn't do enough damage to make up for the fact that it pretty much must be cast in combat.
Faerie Fire: Good for dealing with invisible foes assuming your cleric or wizard can't. This is too situational and weak to bother with otherwise.
Rot of AgesDrM: lol no sneak attack 4 u. Too bad about the short duration, though. This spell is stone cold terrible, I don't know what I was thinking.
ThunderheadSC: 1d6 damage per round/level unless they make a reflex to negate, and also acts as a tracker against targets who turn invisible This does ONE damage per round/level, and you can't cast this on a foe you can't perceive. I can't imagine any situation where you'd be happy you prepped this for the day.
2nd Level
Bear's Endurance and Bull's Strength: As useful for a druid as it is for everyone. Bear's Endurance will be your main in-combat healing spell for low levels; just keep people alive until you can use Vigor. Grammar fix
Blinding SpittleSC: Absolutely broken. Blindness with no save, with a ranged touch attack at -4. Why do they keep reprinting this spell? Typo fix
Blood SnowFrost: Only prep it during the winter or when in an arctic or otherwise frozen area, but d2 Con drain/round is awesome when you combine it with battlefield control spells or flight effects to make sure your enemies have to stand in it.
BramblesSC: Excellent weapon buff, especially coupled with Shillelagh. After the CD/SC nerfs to this spell, it is overrated in the extreme. It's strictly worse than Shillelagh, and doesn't stack.
Creeping ColdSC: A great attack spell, and replaces Produce Flame as a blasting spell.
EarthbindSC: Ground those fliers. Kelpstrand and Gust of Wind do this and much more besides.
Gust of Wind: Very underrated utility spell. Clears fogs, blows away small foes, extinguishes torches, and disperses swarms. On top of all of this, it just plain wins any fight with any flier smaller than large.
Halo of SandSand: Yet another druid AC buff. This one is deflection, though, so it stacks with Barkskin and armor and helps against touch attacks.
KelpstrandSC: I like to think of this spell as webshooters. If it's not huge, it's pretty much just screwed. Your grapple DC will exceed that of most enemies who aren't grappling specialists or very large and very strong, and even if they are they'll need to spend at least one round bursting each strand of kelp. This spell is silly broken.
Master AirSC: Self-only flight, with short duration. Still handy, though. Winged Watcher is lower level and does 95% of what this spell does.
Nature's FavorSC: Excellent (swift!) animal buff spell; cast it on your Animal Companion or summons. No real need to go into previous versions any more, since SC is pretty much definitive.
SplinterboltSC: It's druidic Scorching Ray, but with no SR. Three 4d6 damage bolts with a 18-20 threat range isn't half bad.(Thanks jackmojo) Grammar edits
Wild InstinctsRoE: +1 to spot and listen just for preparing it. Casting it is kind of useless; a min/level ability to give you Uncanny Dodge is only useful when you know you're going to be surprised. Some playtesting realizations
3rd Level
Attune FormSC: Immunity to planar effects for caster level/3 characters. A handy spell for planehopping games, and much more useful than the lower-level Avoid Planar EffectsSC, due to the longer duration. Grammar edits and some fiddling
Call Lightning: This is a good lead-off for long or unchallenging fights, as it gives you lots of turns of attacks with okay damage. Prep one or two a day and use it as your fallback when your specialty (be it summoning, melee, whatever) isn't the best tactic.
CrumbleSC: Apparently druids get Shatter at third level. It's still handy.
Cure Moderate Wounds: Should be self-explanatory. This is not a good spell at second level, why the hell would you cast it at third? Not sure what I was thinking.
Energy BarrierKey of Destiny: It lets you put up an immobile protective barrier against acid, cold, electricity, fire, or sonic energy and their residual effects (e.g. fire: also blocks heat, acid: water, cold: snow, etc.). This amorphous barrier can completely surround you if you like and the duration is "concentration +1 round/level," which could be huge in some circumstances. If your DM allows Dragonlance materials, this is a great protective spell. This is a super situational third-party variant of Protection From Energy. Why is it here?
Entanging StaffSC: Free action grapples with a +8 bonus. Great for when you're out of Wild Shape for some reason or if you're using a Shillelagh-enspelled staff as a Legendary Ape. Spikes sucks, so this gets an edit.
Evard's Menacing TentaclesPHB2: Assuming you have a good strength bonus from a Wild Shape form, this spell provides some battlefield control, metes out some damage, and gives a climbing bonus to boot. Grammar edits
ForestfoldSC: +10 on Hide and Move Silently checks in a natural environment of your choice.
Giant's WrathSC: An interesting alternative to Call Lightning. At early levels, the lack of a need for an attack roll, the lack of DR issues, and the greater number of uses per cast makes Call Lightning the better choice. At higher levels, though, the high strength of Wild Shape forms, the caster-level based damage bonus, and the lack of SR on Giant's Wrath helps it catch up.
Heart of WaterCM: The winner in a so-so spell family. The main effect of swimming/gills is handy when you get the spell, and on-demand swift-action Freedom of Movement is perfect for a bad grapple or failed save.
JunglerazorSC: Does 1d10/level (up to 10) in a 120ft line. Because it's target specific, shoot through your friends to damage only plants, plant critters, vermin, fey and animals. This is super situational. I'm not sure if it's worth listing.
Plant Growth: This is druidic Solid Fog, as long as there's some undergrowth. Alternately, make yourself every farmer's friend. Some more detail on what it does
SpikesSC: Improved Brambles. Higher attack, better threat level; what's not to like? How about the fact that it doesn't stack with anything and just plain blows? Don't cast this spell.
Swift Lion's ChargeMiniHB/Lion's ChargeSC: Pouncing is very handy, but this spell can start to eat up spell slots pretty quickly. A similar, overpowered spell named Lion's Charge is in Savage Species, and, while it isn't swift, it gives the Pounce ability for a duration.
ThornskinSC: Good as a wildshape buff, especially for grapplers, since even trying to escape hurts your enemy. This is two levels higher than Babau Skin, has a shorter duration, and does less damage. And Babau Skin isn't very good.
4th Level
Arc of LightningSC, Blast of SandSand, and Flame Strike: The last blast spells worth casting. Flame Strike is a staple and core. Arc of Lightning and Blast of Sand have more-specialized areas of effect (Arc of Lightning is sure to hit two guys and pretty much nobody else, whereas Blast of Sand's 30' cone is Very Large), ignore SR and benefit from Spell Focus (Conjuration). Blast of Sand is probably the most useful due to its large AOE, but it caps out at 10d6 whereas the others cap at 15d6. All of them have situational advantages (and none of them are more potent than Boreal Wind), so choose the one best-suited to your game. This replaces the individual writeups on these three spells, since they're pretty interchangeable.
Aspect of the WerebeastRoE: Nothing about this Shifter-only self-buff says it only works when you're in a humanoid form, but it is severely limited by its round/level duration. Prep it instead of Bite of the Wereboar anyway, and use Tiger aspect exclusively. Round/level pounce that you can share with your pet is delicious.
Boreal WindFrost: This is a mix of Gust of Wind and an AOE blast. In a fight, the damage is okay but lasts for multiple turns and enemies who don't save have a hard time approaching you, and out of a fight, this has a bunch of interesting utility and RP uses. This is a stylish, versatile, and powerful spell.
Claws of the SavageBoVD: Got claws? This gives you a +2 enhancement bonus on them, and also gives increases your claw damage as if you were two sizes larger. It is an Evil-typed spell, though. I should really learn to read durations. This is higher level than Greater Magic Fang and only slightly stronger, while being inexplicably evil to use and shorter duration. Bleh.
Superior Magic FangSC: GMF on all of your attacks. It's self-only, though. Aaaand has a really short duration. Not worth the in-combat action.
Vortex of TeethSC: A spell that does force damage, and can tear apart anything that can't get away. This makes a mess of anyone caught in Entangle. Typo fix
5th Level
Animal Growth: Multiple animals (your pet and any summons running around) get bigger and get some nice bonuses. One of the best buffs in the game, let alone in core. Typo fix
Baleful Polymorph: Turn your opponent into something inoffensive. Toad is a classic form that offers no advantage to your target. This is the core option for transporting Animal Companions in cramped quarters or inappropriate environments Pokemon-style, since, as a permanent spell, it's dispellable. Classy tricks include polymorphing your Roc Animal Companion into a raven for cramped quarters, or polymorphing your T-Rex companion into a frog to go underwater. Some grammar fiddling
Call Lightning Storm: Call Lightning, only more so. 5 dice of damage instead of 3. This is emphatically not three spell levels better than Call Lightning. Not worth bothering with.
Choking SandsSand: Miasma, only less so. Alternately, nonpsionic Crisis of Breath. Good for shutting down a caster for a turn. Far too situational. It's neat that this always works, but nothing about the spell says someone can't still talk/spellcast, just that they can't breathe. Most opponents can hold their breath for the duration of a fight.
Cloak of the SeaSC: When you're underwater, it's Water Breathing, Freedom of Movement, and Blur, all in one neat little (long-duration!) package. A must-have for any underwater adventures.
Owl's InsightSC: A long-duration scaling boost to Wisdom with an unusual bonus type? A must for focused druidic casters, although summoners and wild shapers can give this a pass, since it doesn't do anything but raise spell DCs.
Phantom StagSC: Phantom Steed, only two spell levels higher and with slightly beefier stats. Since druids already have always-on flight at this level from Wild Shape, this is mainly useful for the Etherealness ability it gains at 18th level. This isn't that great except for the etherealness.
Quill BlastSC: After the Spell Compendium rewrite, this once-broken spell is now not quite as hot. It still outperforms typical blasts for a couple of levels, but by level 9 blasting is probably not the most optimal thing to be doing. It is a really mean spell for a GM to use on the PCs, though. It just isn't worth it. Every time I prepped this I ended up dropping it for a pack of crocs or an elemental. Blasting just isn't that great at this level, especially self-targeted bursts.
Ice ShieldFrost and Stoneskin: Excellent defensive spells (Ice Shield is stronger but has a shorter duration), but both are too monetarily expensive to use too often. My home group houseruled that the monetary costs off of these spells and I still didn't cast them much. They're just not that great.
Tree Stride: Teleport, but self-only and your GM can arbitrarily limit your use of it, since you need a chain of trees to travel long distances. It's still good.
6th Level
Bite of the WerebearSC: Bite of the Weretiger only moreso. You'll probably be fine simply prepping Bite of the Weretiger instead; this spell offers relatively small benefits over that spell.
DrownSC: Save or dying (0 hp). Handy for capturing enemies alive. Not death magic, but obviously doesn't work on non-living creatures, water-breathers, or creatures with no lungs. This has replaced the repeatedly-nerfed MiasmaSC.
Enveloping CocoonSC: A reflex-based save-or-lose, force-based to boot. Unfortunately, it doesn't work on anyone who can cast Dimension Door (or any similar non-somatic escape spell), anyone who has a natural weapon or a light weapon in hand, and unless you just want to trap them for caster level/rounds, you'll need to follow it up with another spell (like Baleful Polymorph).
Fire Seeds: Excellent trap spell when used to make holly berry bombs. Couple it with some sort of fire resistance or immunity and you have a killer emanation-from-yourself nuke. What was I thinking? Fire damage at 11th level? Blasting at 11th level? No, no, no, no, no.
Greater Scrying: Scrying without the long casting time and relatively short duration; the minor spells you can cast through the sensor aren't that useful. So why don't you just cast Scry?
Tortoise ShellSC: Basically, Greater Barkskin. Not as good as Greater Luminous Armor, but is natural armor instead of armor. A level 6 spell for only +1 AC over a level 2 spell? I know it scales upward, but this is drek.
7th Level
CloudwalkersSC: 10 min./level flight for the entire group. This is getting into the "If you can't fly you can't play" levels, but it is handy for anyone who hasn't gotten their wings yet.
Master EarthSC: Quite nice as it allows teleportation, a rarity for druids, unerringly to any location touching the earth. As it doesn't have the teleportation descriptor, it can thwart problems such as Forbiddance, Dimensional Anchor/Lock, etc.
Word of BalanceSC: Somewhat unreliable because of the odd alignment restrictions, but very powerful when it works.
8th Level
Red TideSC: Save, and you're prone and have a -2 to pretty much everything. Don't save, and you're limited to move actions and poisoned with a nasty strength-damage poison. Save-and-you-suck-anyway is always a good choice, and this is a huge 30' radius burst.
StormrageSC: Flight, the ability to throw respectable lightning bolts, and immunity to projectile ranged attacks and wind effects of all kinds. This is more of a spirit shaman or cleric spell due to the flight, but the immunities are helpful.
Word of Recall: A quick escape spell, and one of the very few teleportation spells available to druids.[/spoiler]
-EDIT- I did a second wave of updates to this on a post on page 5 of this thread.