you can check this out: http://www.ianfernando.com/2009/wordpress-craigslist-classipress/ or http://www.sitemile.com/classifiedTheme.php
you can have the new wordpress classified theme from sitemile, has just been update for version of wordpress 3.1, has google maps integrated with streetview, ajaxified image uploader, paypal integration, and everything, custom post types, etc. Check it out here: http://sitemile.com/p/classifiedTheme
DO NOT BUY ClassiPress I bought this theme in hopes of creating craigslist style ad site. It was quickly abandon because it lack everything need to create craigslist style site. Just for starters.One would need to create 3000+ Category just to post items buy State/City e.g. there would have to be 1 category for USA then 1 sub category for the state of NY then 25 subcategory under that for cities. so imagine having to do this for ever place in the world.
buy the sitemile classified theme: http://sitemile.com/p/classifiedTheme it has all those features and has good support. Also newwer version 6.1.6 is compatible with wp 3.1.2
another version launched 6.1.7 http://sitemile.com/p/classifiedTheme also there is a new version for the wordpress sitemile framework http://sitemile.com/products/sitemile-theme-framework/
We have another update for our classified theme in www.sitemile.com I can offer custom work to make it look exactly like craigslist, just use the contact for in the site to get in touch with me.