Actually, it's a good point that we should have the benefits of these classes, so here's a few.
Fighter: One of the best non magical damage dealing classes, especially with regards to archery. Though it requires a Barbarian dip to shine as a charger, their feats are useful for that too. Fighters make excellent short dips for many non magic builds. Fighters can also make very effective trippers, though Fighters can't really be effective at all of these at once (Fighters in general can be good trippers, chargers, and archers, but no one Fighter can be great at all of those). Note that the Zhentarium Fighter is clearly Tier 4, mostly due to Imperious Command.
Healer: Hey, they get Gate. That's awesome when you finally get it.
Ninja: They've got a few very cool class abilities... they're just upstaged by most of the other skill monkeys and have too many downsides. But stuff like Ghost Mind is pretty cool, and if you don't have ToB their ability to phase through walls when needed is pretty handy for an infiltrator. If you do have ToB, the Swordsage just does this better.
Expert: Iajuitsu Focus makes these guys shockingly effective in combat for an NPC skillmonkey class. Bust out the Gnomish Quickrazors and go to town... these guys can actually show up the CA Ninja at combat with some work (and party support). Diplomacy and UMD can be very useful (if campaign dependent) skills. And Autohypnosis is likewise a very handy skill to throw in there. Sure, Factotums are pretty much strictly better, but if you wanted to play as an NPC class, this is one of the best (the Adept is better, but the Expert is still solid).
Paladin: The base class is quite lacking, but the variant Paladins can be quite useful. Paladin of Tyranny is an awesome 3 level dip, for example, and combined well with Hexblade 4 (with Dark Companion). Standard Paladin 2 is a lot of fun for Kobold Sorcerer gishes, who can take those levels and still have full caster progression (via Loredrake and the Greater Draconic Rite). Note that the PrC Paladin is far stronger than the regular Paladin, though that's partly because it gives all of the useful Paladin abilities in just three levels while losing you only one caster level. And Detect Evil at will can be very handy in some specific sorts of campaigns.
Knight: Bulwark of Defense is awesome. Too bad there's a maneuver that does basically the same thing, and most of the rest of their abilities are poor. But Bulwark is awesome, and don't forget Diplomacy as a class skill.
CW Samurai: This guy is high in Tier 6, possibly Tier 5, mostly for their incredibly cool level 10 ability. Combined with Imperious Command you can lock down a battlefield if the enemy isn't immune to fear, especially if you've got 9 levels of Zhentarium Fighter. Note that Dread Pirate 5 and Scarlet Corsair 5 give these same abilities (only with a better duration, making them far superior), but if you didn't want to be a pirate or oceans aren't in your game the Samurai is the only way to get AoE intimidation like that. There's also potential for an Orc Warlord who's immune to fatigue combined with Intimidating Rage and Imperious Command. Also, the CW Samurai does have Diplomacy as a class skill combined with Charisma synergy.
OA Samurai: Basically a crappy Fighter, these guys get Ancestral Relic as a first level bonus feat without having to be good and diplomacy as a class skill, plus another good save, but they get fewer bonus feats off a smaller list. They're a great one or two level dip. Most importantly, they've got Iajuitsu Focus as a class skill, and that ability is very handy, especially if you PrC out into Iajuitsu Master.
Monk: Though horrible as a long class, these guys are an awesome dip. Monk 1, Monk 2, and Monk 6 are all solid break points, providing many bonus feats, full saves, and Wis to AC (which Carmendine Monk or Kung Fu Genius can turn into Int to AC). This class goes great with Shou Disciple, which progresses flurry and gives full BAB. The class is heavily upstaged by the Unarmed Variant Swordsage, but it's still a solid dip. Consider Monk 6/Shou Disciple 5/Kensai 9 or Monk 6/Shou Disciple 5/Unarmed Swordsage 9 as solid examples of a fighting monk build. Monk 1/OA Samurai 1/Warblade 8/Shou Disciple 5/Iajuitsu Master 5 is another solid build. The combination of Sense Motive and Diplomacy on a wisdom based class can be very handy... our party will often back up the skill monkeys with a Monk during social encounters, with the monk using Sense Motive to watch the interaction. Monk is also a solid dip with Druid, since you can use iterative attacks with your unarmed strikes while Wild Shaping, and Wis to AC is handy if you can't purchase a Monk's Belt.
JaronK