A few non-wotc books have some neat spells.
Hollowfaust: City of Necromancers (Scarred Lands campaign setting, by Sword and Sorcery) has a few spells, including one that switches your soul with another person, and one that permanently makes your familiar undead, as well as a few nifty items (like a 4500g skeletal hand that allows you to cast spectral hand 5/day) and it also has a few new undead, including superior and masterwork skeletons (more costly to animate than regular skeletons, but worth it).
Relics and Rituals 1 (scarred lands, by Sword and Sorcery) has a few shadow-based spells that rock, and several new prestige classes (including the blood witch who can sacrifice hp to recast spells, the crypt lord, and the penumbral lord). One third level spell allows you to drain strength from a target and kills the target if his str hits 0...at which point he animates as a shadow under your command. A few higher level spells allow you to gain more shadow-type minions.
Relics and Rituals 2 has several new spells that boost undead, including the bones of (silver/iron/adamantium) that grant DR. It also has three sigil spells that permanently make your skeletons ice/fire/acid type (one element at a time only). It also has 2 spells to slow down your aging, and a true ritual (a true ritual is like a spell, but takes more than 1 caster) that kills an entire city and animates all the people in it as free-willed skeletons bound to the area. The non-necromancy spell Weeping Fools is also very nice...a second level spell that renders an opponent helpless if he/she fails a will save. All the person can do is cry for one round per your caster level...really nice, and fits in with the dread effect of the necromancer very well IMO.
Encyclopaedia Arcane-Necromancy: Beyond the Grave (by Mongoose Publishing) has a lot of worthless junk in it (IMO) as it has a lot of house rules stuff that most DMs won't allow. However, it does have a few very useful spells, including the 0 level spell animate animal (gives you an undead animal servent) and the 1st level spell animate skeleton (allows you to gain 1 skeleton, and only one skeleton, as a servent...useful, as most wizards won't get undead until level seven). The book also has a 3rd level spell that permanently boosts zombies so that they get full actions every round, and a couple of neat high level spells (one 7th level spell raises an entire ship and crew to serve you, a 9th level spell raises all the corpses in a city as long as no sentient beings are in the city when the spell is cast, and one 9th level spell that can raise you a fleet of ghost ships and crews to serve you). It also has a second level spell that lets you see through the eyes of your skeletal minions, which I have not seen elsewhere.
Edit: Sword and Sorcery is published by White Wolf Publishing.