Flippa - Flippa is a platform for trading websites.
Domainz.io - Premium domains, for not so premium prices
Transferslot - Easily buy and sell side-projects
Newsy - Monetize your un-used domains and turn them into your own content aggregator with 0 code!
buysellwebsite - Created by two California attorneys, WebsiteBroker.
DomainWatch - Domain Monitoring Made Easy