Another option (although it requires two feats) is getting Fiendish Heritage and then Fiendish Power (both from Complete Mage). Fiendish Power increases your caster level for evil spells by 1. I admit, not a great option, though it would open up the possibility for some moderately useful spell-like abilities or resistance to acid and fire (with the other Fiendish Heritage feats). If you're a wizard specializing in necromancy, then picking up six or nine levels of Master Specialist (also from Complete Mage) would give you a +1 or +2 bonus to your caster level for necromancy spells, as well.