Immediate Magic (Player’s Handbook II) replaces your familiar with an immediate-action, single-round effect that you can use Int mod times per day. The nature of the effect depends on the school you specialize in:

Abjuration: Urgent Shield – +2 AC
Conjuration: Abrupt Jaunt – short range teleport
Divination: Glimpse Peril – +2 on next saving throw
Enchantment: Instant Daze – Daze someone who attacked you in melee
Evocation: Counterfire – 1d6/3 levels force damage on enemy who attacked you at range
Illusion: Brief Figment – Single mirror image of you
Necromancy: Cursed Glance – −2 AC and saving throws on enemy who attacked you at range
Transmutation: Sudden Shift – Gain climb, fly, or swim speed equal to land speed