I meant to start this list a while back as a partial remedy for all the scammer accusations flying around. While the introduction of secure trade will soon make this list obsolete, I hope folks continue to favor those listed here in future trades. They've proven themselves to be decent players:

Duciel
Madbull/Madball (sorry, can't remember your exact in-game name!)
Silentreaper -- though some balk at his prices
NawtyNate
Rannos

These are the folks with whom I've had direct experience. Please add to the list.

Thanks.

p.s. if another list like this exists, I apologize. I was unable to find it.