Well as a sorcerer your implements are also weapons, so you actually have a nice selection of powers available. From the top of my head I would say:
Twin strike(Ranger): If you are a dagger wielder, this power is pure win for you, as a sorcerer your Dex or Str are going to be top notch. Very good.
Dark beckoning(Vampire): This is an implement power, cha based, with improved accuracy and it targets Will. While the damage isn't outstanding, it works for you if you moonlight as controller
Vicious Mockery(Bard): Implement Power, Cha based, targets will, and since it is arcane you can eventually add your bonuss damage if you play your cards right, softening a difficult enemy before dealing a killing blow could be good
Virtuous strike (Paladin): Gain a melee basic attack based on Cha, if you hit you gain bonuses to saving throws.
Spiteful Glamor (warlock): Not bad as an openning shot, you can eventually add your bonus damage.
Eldritch Strike (Warlock): Gain a melee basic attack based on Cha, since it is arcane you can eventually add your bonus damage to it
Basically you are good taking powers based on Charisma, Strength (if you are Cosmic/Draconic) Dex (storm/Wild) or Constitution (Elementalist), you are good taking either implement powers or weapon powers, just remember to pick a power that doens't contradict your character (i.e. don't take melee powers if you are artillery) Pick a power that does soemthing your at wills don't already do (if your at-wills target Fort and Ref, pick a power that targets will, not another that targets Ref). If able try to pick a power that will also benefit from your extra damage (like warlock and bard powers) or a power that increases sinergy with other members in the party (if you have a warlord as leader it will be a good idea to pick a power granting you a basic melee attack)