Here’s a couple of very useful websites if you’re looking to sell your website or just the domain name.

Sedo:
http://www.sedo.com/main.php3?language=us

Names Pros:
http://www.namepros.com/

Check out these posts too:

  1. What is your domain worth?
  2. Get help coming up with a domain name
  3. Interesting Facts About Domain Names
  4. Get your .Me domain starting tomorrow
  5. Who's hosting a domain
  6. Instant Domain Search
  7. Setting the preferred domain