If you join the theives underground they give you a bunch of extra quests. After the Pettbone quest, you talk to the guy in the place just North of the gypsy. He gives you some quests, and after that, you can do quests for the black market guys. Your contact stands in front of Poone's only at night. You can trade stuff in the black market and turn in your loot for booty after doing specific quests. They have one like it in Caladon too.
there are two, one in Tarant and one in Caladon. however, you have to be a member of the Theives Underground to find out about them. they won't deal with you otherwise. there are a number of ways to get into the Underground. there was a post in the last couple days about it, just read through the titles of the last few threads.
