Spell-wise there's:
Spell Resistance (duh) 1min/level, SR 12+caster level
Mantle of Chaos/Good/Evil/Law (Planar Handbook, Spell Compendium) 10min/level SR 12+caster level
Visage of the Diety (Complete Divine, Spell Compendium) SR 20
Greater Visage of the Diety (Complete Divine, Spell Compendium) SR 25