Not dissin' the fogs, it's more of a party issue. I get the idea with the fogs and the "lock down" part is very cool. Lovin' the idea that I can dictate which enemies can attack (or have reduced effectiveness outside the fog, etc...) but what I don't see happening is my party being able to actually do much to the critters that are in the fogs / clouds (at least the fogs / clouds that obscure vision).
While it is often hard for non-casters to do much to people in the fog clouds, it's not always an issue. Just a few examples:
Obscuring Mist - This is really used mostly for defensive maneuvering than anything else. Not directly offensive.
Fog Cloud - This is more to simply confuse your enemies and restrict what they can do. It's not much of an offense, and unless you're looking to buy time, it's not very useful against a single enemy. It's more to confound a few enemies while you deal with the rest. As Rebel said: divide and conquer
Stinking Cloud - This is probably your first "offensive" cloud spell. It has all the benifits of Fog Cloud, plus it forces repeated Fort saves to avoid being nauseated. Nauseated opponents can only take move actions! So, they're probably going to do everything they can to get out ASAP. This helps the non-casters in that they can ready actions to target people as they leave the cloud, if they're on the right side of it. If you're lucky, they will have failed a save in the cloud and be shut down for several rounds after they immerge.
Solid Fog - As mentioned earlier, simple divide and conqure. Two
very important things of note: no spell resistance and no save! So, barring any form of teleportation or etheral travel, someone caught in the middle of this thing will stay inside for three rounds and there's
nothing they can do about it.
Cloudkill - All the benifits of Fog Cloud, plus it really kills things quite nicely. Even more powerful foes risk Con damage, which deals more HP damage the more hit dice they have. Also, it makes them increasingly more likely to fail future saves. The only downside is that this fog moves, so you can't stick guys in place with Web and hit them with this cloud for more than a few rounds, unless you find a way to contain the fog.
Acid Fog - All the goodies of Solid Fog plus some great damage.
Also, note that many other good Conjuration spells have similar 20-foot radius area of effects, and they work well together. Web and Black Tenticles are two great examples. Glitterdust is rediculously cool, but it only has a 10-foot radius. It's too bad you don't have access to Complete Arcane, because the Sculpt Spell feat is really wonderful for these types of things.
