I wanted to grab an RSS feed from every city in the USA for the computer gigs postings. Since most of these jobs were telecommute it didn't matter where the job actually was and this allowed me to peruse all of craigslist.org with ease. You can use it to track any query you'd like.
I no longer do any ongoing development for this project, I have released it under the MIT License on Google Code. If this project was of interest to you please check out the rest of benrasmusen.com.