Surely one of you guys have a shop or a marketplace or something like paid subscriptions. And I need to learn the basics to make sure that what I think I know is actually correct. Anyway..

Do you have a marketplace on your web site/community? And if so, in what form, and how do you promote it? Does it selfsustain? How do you keep it interesting and fresh to get people to re-use it (to come back and put more money in it)

Do you use a seperate section on your site with shopping cart software?
Do you use something that integrates with vBulletin?
Do you use paid subscriptions?
A private forum?

I'm in the process of starting a nyc based site and I am thinking about using one of the amazon affilliate scripts that display the contents on my own url to bump up the google indexing but I found its a pita trying to find one script that works with amazon usa, amazon uk, etc etc.

The other thing I was thinking about doing was starting up a classfieds section for people looking to buy/sell/trade. I haven't decided yet whether this will be a forum or some type of script. For my own convienence, I want everything vb integrated.