A site for people who want to complain about their landlords. It was called DontRentFrom.com, and I only recently let the domain go.
Man, this site would have been great. A lot of people I know (myself included) have previously had bad landlords.
Yeah, I know a lot of people like that, too, which is what gave me the idea. In spite of some Google advertising, though, it never really took off (a few hundred posts total over 2 years or so).