Domainz.io - Premium domains, for not so premium prices
Flippa - Flippa is a platform for trading websites.
Newsy - Monetize your un-used domains and turn them into your own content aggregator with 0 code!
Transferslot - Easily buy and sell side-projects
Tool.Domains - Search free to register expired domains
buysellwebsite - Created by two California attorneys, WebsiteBroker.