I know this sounds awful, but some times I used them as feeders to my more carnivorous fish, or give them to friends as feeders. Got rid of the insane amount of extra fish, and saved me some money on food.
There's a buy/sell section at the bottom of the forum is you want to sell them here or alternativly you can offer them at your lfs but you probably won't get anything for them because lfs's buy them for pennys and have no insurance against outside breeders/sellers.