I've heard good things about Master of Shrouds, and the Mother Cyst feat from LM.
3e Pale Master used to be a passable dip but no longer.
One important thing to figure out early on is what your DM thinks of items, feats, and spells that boost the number of undead you can control. If he or she is dead set against it, you may want to rethink playing a necromancer. Obviously this also applies if one of your fellow players is trying to be exalted, play a paladin, etc.
Something to watch out for: Summon Undead spells do not involve you creating undead, so if you want to avoid the hassle of making a path for your undead minions, you're actually better off as a conjurer.