Afternic.com  
   Domain name auction site with variety of services like domain news, appraisals, and chat. Recently acquired by Register.com.
   http://www.afternic.com/

TopComs  
   Offering a selection of .com domains for auction, along with general domain information.
   http://www.topcoms.com/

eBay.com  
   World's leading auction site has large selection of domains available.
   http://listings.ebay.com/aw/plistings/list/category3767/index.html

Auction2.net  
   UK based site that mostly caters buying and selling of domains with .co.uk and .com extensions.
   http://Auction2.Net/

Easy Name List  
   Domain Auction site. Has categorized listings of domain names for sale.
   http://www.easynamelist.com/

BSV-online  
   BSV aims to be Europe's biggest brokerage company for the trading of domain-names combined with a wide range of supporting services including our unique web-mail system.
   http://www.bsv-online.com/front.htm

Bids4Domains  
   Allows to buy or sell domains at no extra cost. Free advice available.
   http://www.bids4domains.com/

Domain Names and Properties for Sale  
   Displays domains with a unique description for each one.
   http://www.domaincrossing.com