A Java-based application allowing you to monitor auctions you're not part of, submit bids, snipe (bid at the last moment), and otherwise track your auction-site (eBay only currently) experience. It includes adult-auction management, several currencies (yen, pound, dollar, and euro, presently), drag-and-drop of auction URLs, a unique 'multisniping' feature, a relatively nice UI, and is known to work cleanly under Linux, Windows, Solaris, and MacOSX from the same binary.
