I like the Subtle Spell feat, from the netbook of feats. My gnome sorcerer had a good time with it.
Subtle Spell [Metamagic]
Source: Netbook of Feats
You know how to disguise the use of material, verbal, and somatic components; thus making your spell casting difficult to recognize.
Prerequisite: Spellcraft
Benefit: When you cast a subtle spell those who could observe you must make a Spot check opposed by your Spellcraft check to identify that you are casting a spell. A subtle spell uses up a spell slot one level higher than the spell's actual level.
Normal: Without this feat spell casting is automatically recognized as spell casting.
Notes: Casting a subtle spell still draws an attack of opportunity. If the person taking the attack of opportunity fails the opposed Spot check they still get the attack of opportunity but do not know why you let your guard down.