Craigslist is a centralized network of online communities, featuring free Classified advertising advertisements (with jobs, internships, housing, personal advertisement, for sale/barter/wanted, services, community, gigs, resume, and pets categories) and Internet forum on various topics.
I sold my house using craigslist and without a real estate agent. Specifically, the buyer found my property listing on craisglist. I found more responses came through craigslist than for sale real estate ads purchased in the Boston Globe.
If you are looking to advertise your house for sale, this shoud be the first site that you visit.
Hands down the best way to look for a place to live. (At least in the bay area). Too bad they haven't bothered to update their site any time in the last 7 or 8 years. I just wish someone over there would build a better search.