Try CraigZoom: http://craigzoom.com
Here is a way to search for cars broader than just by cities or regions.
(seven states for now):
We just wrote an full-featured ruby library to scrape listings. Too we packaged it with a useful script to automate daily email reports on new posts. Everything’s well documented, and we hope it takes off as the de-facto ruby-craigslist library: Check it out in action here: http://www.derosetechnologies.com/community/libcraigscrape
Searching multiple cities or multiple categories simultaneously is always a panic. This free tools may help you to Search all craigslist cities http://www.seekyouritem.com/cl/
If you’re not looking for global results, you can get SMS & TEXT updates with this tool here: http://www.craigspy.net