Not sure if this is common knowledge or not, but you can use CraigsHelper.com (in firefox) to search how ever many cities/states/etc you want. It's a little klunky, but I find it usefull to use once every couple of days to see if anyone's basement is being cleared out of cabs

Just don't buy the ones I'm interested in... er... j/k!
EDIT:
Please use this tool if you have a firm grasp of basic geography and/or you know how to google city names before bothering sellers (be specially aware of Californians, they can be right ornery. Must be because they are so close to Canada?)