I'm searching for resources on the creation of undead and on undead in general, as I want to develop a new realm for my homebrew setting in which necromancy and magical-alchemical research on undead, diseases, death, decay, ghosts, etc. is the main cultural aspect. These necromancers would create undead monsters by magical devices, alchemical potions, dark rituals, simply stitching several corpses together, or conjuring demons to animate the corpses (which would be in different states of decay). (As an example of my inspirations, take a look at the Scourge / Undead faction of World of Warcraft.)
So far I've found some references in Open Grave: Secrets of the Undead by WotC. But I'm not limited to D&D—I only need the fluff, not really the rules.
My question then is: Do you know any other material on this topic? Which books can you recommend?