I use namecheap to purchase domains. Namecheap also has a marketplace to buy and sell domains. I blogged about this today and put up a minor list of good domains you can purchase there. Hosting and Domain Blog At the namecheap marketplace, there are about 2000 domains for sale right now. Some with a fixed price, and some you can make an offer on. Some are going for a song, some for a kings ransom. Try the namecheap marketplace if you are looking to purchase a domain or maybe sell a domain (believe it has to be registered at namecheap).