The only Craigslist auto posters that actually work are expensive as hell, as Craigslist is constantly changing it's templates and making it necessary for the scripts to be constantly updated.
http://clbotpro.com/ used to work but I haven't used it in years so I can't vouch for it now. If you look at the Craigslist section of Black Hat World you can find people to do occasional posting for you pretty cheap...