Ultimately no. You can query for listings with a search string from an RSS feed such as this:
http://YOURCITY.craigslist.org/search/sss?format=rss&query=SearchString
As far as posting, craiglist has not opened their API. However, this SO Question may shed some light and a possible solution – although not a very reliable one.
Craigslist Automated Posting API?
Write a note to craigslist asking them to open their API,
Craigslist does have a “bulk posting interface” which allows for multiple posts to happen at once through HTTPS POST. See:
http://www.craigslist.org/about/bulk_posting_interface