Mage of the Arcane Order (complete arcana)Full spell casting, some other stuff.
Spellpool works just like Spell Storage, only you cast into the pool within 24 hours of calling a spell from it. You can call up to (CL/2) spell levels per day from it.
*
Ultimate Magus (complete mage)Full spell casting with a feat, freebie metamagic enhancement.
Nets 9 levels of a 'real' spontaneous casting class at the cost of two levels of wizard. for beguiler or sorcerer & one feat slot for Practiced Spellcaster for the mentioned class.
*
Magelord (lost empires of faerun)Full spell casting, +3d6 sneak attack.
You can convert any prepared spell into any mastered (which may be metamagicly enhanced) spell via CORE's Spell Mastery feat.
Added bonus, an extra 4 spells are added to your Spell Mastery list.
*
Shadowcraft Mage (races of stone)Full spell casting, 40% concealment 24/7.
While the class does not really grant spontaneous casting, it does allow you to turn the ___ Image spell chain into shadow conjuration/evocation-like spells. Spells mimiced are one level lower than the image spell used to create it, and are only 20%+(10%*level of image spell used) real.
The Earth Spell(RoS) bumps Empower Spell up a level, including beyond the cap, so you can use an empowered silent image spell to cast a 110% real 9th level divine evocation spell Miracle which in turn lets you cast any 8th level Divine Spell using one of your 9th spell level slots.
*
Dweomerkeeper (complete divine web enchantment Download it here)Full spell casting, 5/day ignore components, AoOs, and spell resistance.
Allows you to pick up to any 5 spells, you may spontaneous cast them by using a spell slot of equal or higher level.
*
Primal Scholar (secrets of xendrik)¤
Ancient Secret lets you chose a spell so you can spontaneous sacrifice others for it or even burn unfettered heroism's granted action points to recast spells.
*
Hathran (player's guide to faerun)¤
X/day Place Magic, which lets them trade any spell out they have prepared for any spell in their spellbooks. While inside of Rashemen, you can use Place Magic all day long.