The Renegade Writer Markets Wiki isn't just a place for you to look up market listings - you can also contribute. You can start browsing for markets the minute you hit their website, or sign up for an account to be able to add and edit information.
My cynical side wonders how frequently people will actually contribute, but I see they have. Not only do you get the typical information for each listing - pay rate and material sought - you will also find notes about personal experiences with the market. I like that - and I also like that they feature some markets I've never seen before, and most seem to pay well - $.20/word and up so far.