This module creates a drop-in, plug-and-play textual classified ad node type (ed_classified).
The Drupal Classified Ads module provides a quick and easy way to host textual classified ads on your Drupal 6.x and 7.x sites, with obsolete versions are also available for Drupal 4.7.x and 5.x. If you run multiple sites, or don't want to be bothered piecing together a classified ads type, this may be just the ticket.
Project page and official releases: http://drupal.org/project/ed_classified
Project news: http://features.osinet.eu/classified-ads-news
Notice: documentation below only applies to Classified Ads 1 and 2, needs to be reviewed for Classified Ads 3 (6.x-3.x / 7.x-3.x).
Paid classified ads may be implemented by installing the lm_paypal module and limiting ed_classified node creation to paying users. Other schemes may work as well, but the ed_classified module does not handle paid ad creation for you - this is beyond the scope of the module at present, although lm_paypal integration is planned for a future release.
Photo ads may be implemented using image.module, upload_image, and other image modules. I use upload.module, image.module and upload_image combined on my sites, and that combination works pretty well. If you have upload.module, the ed_classified module will allow you to override the attachment form description text on classified nodes, supplying administrator-supplied text - this helps users understand what to do in order to create a photo ad.
Copying node.tpl.php to node-ed_classified.tpl.php in your theme directory will allow you to tailor the ed_classified body output.