ATHATH's optimization log 2, electric boogalo:
Pathfinder stuff!
The Sahir-Afiyun feat gives you some drug-themed spells, but not enough to really make it worthwhile.
The Dreamed Secrets feat lets you, once per rest, choose two wizard spells that are one spell level lower than the highest divine spell level that you can cast and them add them to your list for 24 hours. You need to make a save (and risk some wisdom damage) in order to cast them, but this feat is still really good. And all it took was worshipping an outer god or a great old one!
Arcane Savant gives you some spells fast, but makes you loses a caster level.
Collegiate Arcanist gives you a druid spell every level without losing you any caster levels. The druid spell has to 2 levels lower than the highest spell level that you can cast at, though. It also has some stuff related to Spell Mastery, but that stuff seems kind of meh.
Agent of the Grave makes you lose a caster level and doesn't give you much until you hit the capstone, but having your INT mod's worth of necromancy spells is... okay. What makes it interesting (and thus on this list) is that it has a "dual-capstone", of sorts- in addition to the spell list expansion, you also gain the ability to retain your intelligence after becoming an undead creature and the ability to not be enslaved to the creature(s) that turned you. You lose your class levels if you do this with some types of undead, but a member of this class could have theoretically been around since before the plague.
Veiled Illusionist gives you one Sorc/Wiz Illusion spell per level without making you lose any caster levels. Good stuff.
Soul Warden has some really appropriate fluff (you're an anti-undead commando) and gives you a slew of anti-undead abilities, including positive energy channeling (only the "harm undead" version if you don't have another source of positive energy channelling, IIRC, but the prestige class gives you some other ways to spend its charges) some neato anti-undead spells, and other miscellaneous abilities (including some that control undead). Of note is the ability to regain a charge of channel damage whenever you kill an undead creature with a spell or with channeling once per round up to your Soul Warden level (in?) times per day.
Daivrat gives you only one spell, but it can be ANY spell (up to the level cap that the feature has), can be changed once per day, and gives full spellcasting progression.
Dissident of Dawn gives you nine spells and no casting progression loss if you dip it. It seems pretty good.
Samsarans have the Mystic Past Life alternate racial trait, which can give them some extra spells known (at ANY level) at first level. I might choose them for the build, but I haven't properly checked them out yet.
There's an animal companion archetype that gives you a few extra spells. You can sneak into it as a non-Druid with 2 feats, I think.
I'd like to thank these two guides for speeding up my search greatly:
http://www.giantitp.com/forums/showthread.php?296803-Pathfinder-mini-guide-Casting-spells-from-other-listshttp://brilliantgameologists.com/boards/index.php?topic=2777