There's a link to such a site, right above the post box thing on this board.
As for old figs, There's the site from above for one, the users often times sell their figs, but do know they tend to charge what the fig is worth, ie get as much as they can for the thing.
There's also http://auctions.yahoo.co.jp/
which is like ebay, without as much bootleg shit, you'll also probably need a proxy bidder to buy from it.
Which is run by people who own real life shops that buy figures, and they list stuff they get in on their site, it's worth checking in on from time to time.