AJ Auction Script offers flexibility and feature rich options that are
simple to deploy and easy to manage. Its features include HTML
templates for easy design changes, the ability to create an unlimited
number of categories and sub-categories, Multiple Payment Gateways,
Extended Search Options, Full bidding and buy it now options,
Versatile User Management options and so on. Its features are updated
frequently and freely distributed.

Sources: http://www.ajsquare.com/products/auction/index.php