More spells per day?

[Biggus]

Soooo...nothing a rational GM would allow. That's a shame.

There are non-cheesy ways to get a few more, but not in large numbers. The Spellcasting Prodigy feat I mentioned is not overpowered in its 3.5 version. Various spells can help free up some spell slots for important missions; 24hr spells like Greater/Superior Resistance can be cast the evening before, or a relatively inexpensive Metamagic Extend Rod can make them last 48hrs. At higher levels the same goes for 1hr/level spells like Mage Armor.

[MaxiDuRaritry]

Aeshkrau illumians can use Str for spells per day. Lots of ways to boost Str.

[NigelWalmsley]

Reserve Feats don't grant you any additional spells, but depending on the power level you're playing at they may provide an adequate alternative. If all you're looking for is something to do with your actions that's better than "I shoot them with my crossbow", Fiery Burst and company are fine options.

It's not even broken if you remove the spell Unfettered Heroism from the game, which you should.

Depending on the power level of the rest of the group and how you play it, it's not even all that broken with Unfettered Heroism. If you're using your unbounded spell slots to cast combat spells (rather than things like Fabricate or Charm Monster) it's really a lot like being a Warlock. Most spells are simply not all that problematic to have at-will. It's just that the ones that are problematic are absolutely game-breaking.

[Clementx]

Bestow curse (and its greater variant) can grant anything of equivalent power to the listed effects, and since |-6| = +6, that's a bonus you can gain, as well. And as both the regular and greater versions aren't the same effect, they stack, just like the penalties would.

Sudden Maximized, Sudden Empowered awaken could get you a nice, fat 27 Int if you polymorph into an animal, first. Sudden Intensified awaken (if there was such a combo) could get you a 36 Int.

Fiend of possession can get you a +4 profane bonus.

Do you want to be an owlbear? Because that's how you become an owlbear.

[Kelb_Panthera]

arcane manipulation from lost empires of faerun can get you a bunch of lower-than-your-highest-level slots by breaking up your higher level slots for them. Trade maximum output for staying power. Couple with a ring of wizardry to just never have to even think about "do I have enough low-level slots" again.

Runestaves make for greater versatility with the slots you do have. Can't recomend them highly enough.

[Gruftzwerg]

If you want to get books thrown at you, I can help you out with that xD
Don't search any further, the world most OP weapon is there to help you out: +1 Spell Storing Shuriken

Cast those spells that you still have at the end of the day into the Shurikens. For 8301g you get a full set of 50. You can buy lesser if you want. A single one cost only 166.02g.
Not cheap (early levels), but not expensive either (later levels). Thus a good way to get more spells (that fit with Spell Storing) on those days where you need em more than usual. Finally, you can Full-Attack with shurikens (and TWF if you have the feats). If that doesn't cause your DM to ban Shurikens once and forever I dunno..^^