Still spell, Silent spell, and Eschew Material components. - These three will not over flashy can really get you out of a jam. For my own sorcerer I've found still to be especially helpful.
Sculpt Spell + lightning bolt - this gives a lot of flexibility, and flexibility is power.
Empower - just really useful.
Extend - depending on your spell selection this can be useful. Melf's acid arrow really gets a kick out of this one.
Elemental Substitution - most people would say sonic, but I'm going to go agains the grain, here especially if you take fireball. If you take cold, then you can get through to most creatures with either fire or cold. Cold has another advantage, becuase I've found that I've often been in places where I didn't want to do a lot of damage to the interior and cold has the least effect of all the elemental types on objects. If you were to take the feat twice, then I would say sonic, for the regular damage on objects, but thats just me.