One of the places that I've scored some of my best goth fashion finds is on LiveJournal. In addition to the journals themselves, there are communities one can join, and two of these are GothFash and GothMart. Basically, these communities allow members to post pics and prices of things they are selling, promoting private sales between LJ members. You don't have to be a member of either community to purchase things, but I believe you do have to have an account with LiveJournal in order to post comments and questions. Fortunately, the basic account is free, so not a problem. :-)
I've gotten some truly fantastic bargains on these sites, especially GothFash. You do have to watch where members live, as some are in other countries, so the items might be cheap but the shipping deadly! In addition to traditional goth fashion items, some members also offer items for those interested in lolita, visual kei, cosplay, etc. You can also find makeup, magazines, CDs, DVDs, purses, collectibles, and other fascinating goodies.
Take advantage of this opportunity and check it out today. Just don't buy any of the things I want, okay? Thanks! ;-)