The auction is free, except for buying the fish, and I would imagine you may find almost every kind of cichlid available in the world.
There may also be vendors still selling from their rooms that day. There is always a bulletin board with their numbers and what they are selling, somewhere near the auction room.
I have already bought 2 species from people selling at the auction. If you go to the American Cichlid Association web site, there are some species lists posted.