How do I sell my unused domain names?

There are a bunch of sites where people try to buy and sell domain names, but in my experience, the best bet is to have a modest "for sale" graphic on the page that the domain serves up, but actually have some content of some sort, even just 2-3 paragraphs. Then the domain has SOME "existence" on the net, and has much greater value than if it's just a word. Make sense?

This helps the buyer too because hopefully the one page you have hosted on the domain is no longer in the sandbox and when the domain transfers and goes through the Google hiccup (Google checks domain name record change dates as one of its many variables for calculating search engine results placement) it'll come out in a few days or weeks, rather than a few months.

Two of the best sites I recommend for people interested in buying or selling domain names are AfterNIC and Great Domains.

Believe it or not, a lot of people also sell domain names on eBay. Just use the "reserve" feature to specify a minimum winning bid, but start bidding really low and see what happens. Be realistic, though. Most domains sell in the range of a few hundred or lower, though a very small few of them can sell for astronomical numbers. Try this link to see some of the almost 4,000 domain names for sale on eBay as I write this answer: Home / Buy / Computers & Networking / Other Hardware & Services / Domain Names

When you do get a buyer lined up, I do strongly encourage you to use the services of Escrow.com to ensure that neither party gets ripped off. Once you change the ownership of a domain record, there's no going back...

Hope that helps you out!