Domains123 (Popularity: )
http://www.domains123.com Sells domains across many categories and allows visitors to list their own domain names free of charge.
Name Finder (Popularity: )
http://namefinder.com/ Lists a large selection of domains categorized by genre. Provides seller listings for a fee.
What A Domain (Popularity: )
http://www.WhataDomain.com/ Nearly 1000 domain names for sale, lease, or joint venture. Domain name consulting services also offered.
OnDomains (Popularity: )
http://www.ondomains.com/ Business domain names for sale or lease. Also offering listing services, hosting, shopping carts, and web design.