I am currently looking for some input on the idea of running a classifieds section on a website.

Has anyone ever run such a system on their site with any success?

Charging a nominal fee to list an item or perhaps even an auction module?

Site has a large base of people in a region all interested in the same topic.

In this instance do you just set up a BB type listings they case use for free or do you attempt while not being greedy about it monetize this aspect of the online community?

What have been peoples experiences?