I have seen a lot of talk about how pure spell casters are far more powerful then any other class. To counter this problem wizards published Tome of Battle, which makes the others classes better (or so I am told). I was wandering if there was a way to just nerf the spell casting classes, so they are at the same power level are the rest of the classes. I have thought about just just knocking down the spells per day, or only letting them cast spells from a few schools/sub-schools. But I fear that doing so may make the player feel to useless. So any advice/variant rules/ideas would be helpful!

Try limiting the number of spells castable per encounter. One of the main reasons that spell casters go through the roof is because they can "go nova" for an encounter, blowing off all spell slots in it.

Another thing you could do is give them normal spell advancement, but halve their caster level for all spells. This second option might make them too weak, however.

Have you tried http://www.d20srd.org/indexes/variantMagic.htm or Unearthed Arcana?

Knocking down spells per day is not the solution. It reduces the number of times a day the caster makes the rest of the party useless, but does so by making the caster useless numerous times per day. This is not a good solution. If you want to improve the game, you need to reduce the amount of time any player is standing around, twiddling his thumbs, watching everyone else have fun.

Any real caster fix has to start with the spells themselves. It isn't the number of times they can cast the spells, but the sheer game-stopping power of the spells themselves. Unfortunately, you can't blanket-fix them, because the game assumes you have some of them available at given levels. Therefore you must go through the spells individually to figure out which ones are fine as is, which need to be nerfed, and which need to be removed entirely.

EDIT: I'd recommend checking out Arcana Evolved for a good example of a pruned spell list.

And does little to nothing to alleviate the problem (many "win" spells are not or only weakly affected by caster level) or is contradictory with itself (minimum caster level being equal to [spell level*2 -1]).

A thematically focused spell list might work; Dread Necromancer, Beguiler, etc are usually accepted as non-overpoweredd full casters.

I would have to agree, that going at the spells individually might work out. Just keep in mind, however, that even if a Wizard was some how put into balance with the others, their ability to do things the others cannot possibly do still makes them more "powerful" and in some peoples eyes more fun to play. My opinion though, is this is a worthless cause. In the trek to make even the none casters and casters, the casters will inevitably become useless or just as bad lose their flare, their flavor. Their sole purpose is to cast magic! Magic is inherently more powerful and more flavorful than melee, than swords and armor. Its inescapable. Trying to avoid that is like denying the suns existence.

Tome of Battle has shown that melee can be very fun and flavorful. It does not need to be "I power attack for five. I power attack for five. This time, I power attack for six!"

Arcana Evolved has shown that magic can be made no more powerful than the melee classes, but still be flavorful and interesting. More flavorful, in many cases, than the core casters ever were.

There is no reason casters should have more fun than meatshields. If they do, that's poor game design, and isn't excused by appeals to the "specialness" of magic.

And yet, even AD&D managed to balance them better than.

That's a ridiculous statement, BTW. If magic permanently drains your life force every time you cast a spell, and the spells don't do anything dramatic, suddenly it's not very powerful.

Jack mentioned Arcana Evolved; that has a vastly better balance between casters and non-casters than 3.5. It's really the spells that are at fault; there's just so MANY of them that are problematic.

Easiest casting fix is to ban the 'Big Five'; Cleric, Druid, Wizard, Archivist, and Artificer. Without them, there remain no casters that can do everything at once all the time, and the game works a lot better. Assuming, of course, that nobody does anything dumb like try and include Monks and Fighters and such in the same group as Swordsages and Duskblades, but that should be obvious.

To fix the situation, you have to understand the situation. When people talk about "overpowered casters," odds are they're talking about the Big Five:Archivist, Artificer, Cleric, Druid, Erudite, Wizard (I know that's six). If you cull those classes, there are plenty of classes to replace them.

The basic problem with most of the Big Five is that they essentially have an infinite spell list to draw from, allowing them nigh boundless power if you use those spells to full effect. Sorcerers are generally fine because they have X spells, period, and they cann't change into the perfect character for the day every morning, or pull out the perfect ace every time. The Big Five can. When you're talking about Beguilers, Dread Necromancers, Wu Jen, Shugenja, Ardents, Psions, Warmages, Warlocks, you've really brought casters more into the realm of sanity.

Then, all that remains is to fix melee.

Now, if you're trying to balance the Wizard against the Fighter, stop right there. The Fighter (and perhaps the Monk moreso) is hideously underpowered. Just throw out the pure Fighter (and most other pure melee classes pre-ToB) in favor of Warblade and you just pretty much fixed melee, bringing them in line with the reasonable casters.

So, in short? The caster fix does not involve nerfing casters. It's to cut out the worst offenders and bring in Tome of Battle for melee.

Or make a short list of spells that are troublesome, and simply ban them: Shapechange, Gate, etc. Get rid of silly Persistent spells while you're at it.