Easyroommate.com
#1 roommate site on the web. Largest # of listings, current listings only. Free to search listings in your area, free to place an ad for a room or roommate. Find a room or roommate at easyroommate!
http://www.easyroommate.com/index.cfm?ac=reals

Roommates.com
1,000s of listings with photos and maps. Computerized matches or browse the Internet's largest Roommate Database and find your perfect roommate with a click of the mouse.
http://www.roommates.com/