There is one I have used and recommend called ClassiPress by AppThemes http://www.appthemes.com/themes/classipress/
It comes loaded with options straight out of the box. Take look at how I have used it here: http://centralvictorianclassifieds.com.au/
It is a premium theme but they give great support for it.
You may like it, you may not... Hope that helps.
thanks, looks good as i just want an easy no mess setup. i'll check it out more
tim