www.d2jsp.org is for the d2jsp bot, but they have a rather large trading forum. Only downside is its slow loading. Oh, and their database corrupts every 1 month

www.dtrades.org is a pure trading forum. Here you can buy stuff with actuall money (if i hear anyone doing this i will mock them for all eternity), or trade. It's a lot faster, but it's database crashes once every 2 weeks.