Tomb and Blood:
Mage of the Arcane Order PrC represents an organization, and their order is generic enough to fit into any campaign. There is more info besides the PrC on the Order.
Bleak Academy: necromancer spellcasting academy. Also generic to fit most anywere.
Magic of Ferun:
Guild Wizard of Waterdeep: more specific than MotAO, with some specific history.
Scared Lands Setting:
Order of the Phylantric Valt (Relics and Rituals 2) offer some off color specialization.
The setting also has two warring necromancer cites, with some details on training. (setting core book)
Those are all I can think of off the top of my head. Tome and Blood is probably your best bet.