Ebay worked for me. I made several hundred pounds selling my old stuff. Of course, I then promptly spent the money buying new stuff .....
I'd recommend accepting payment by Paypal only. It stops you having the hassle of banking cheques, and weeds out some of the less attractive buyers. It does cost, but for me the price was worth it to avoid the aggravation.
Ebay has a pricing system for listing that works in bands. Check where the bands are. Listing my items at 1 pound cost me more than listing at 99 pence would have, for instance. They also sometimes do special offers, so if you are not in a great hurry you might want to wait for one of those.
You might also want to limit your sales to people in your country. The international postage costs often puts off foreign buyers anyway, and if you miscalculate the postage and have to cover the difference yourself it can become very expensive (as I found out the hard way when I sent my 2nd edition stuff to Canada from the UK).
Having said that, you could offer them to people on these boards, or over at Dragonsfoot or Wizards of the Coast. Depends how much you trust thses guys (and how far they are willing to trust you ....)
