One of my favourite programs JBidWatcher has moved into version 0.9.9.JBidWatcher is, according to its author, 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 experience. It includes adult-auction management, MANY currencies (yen, pound, dollar (US, Canada, Australian, and New Taiwanese), Swiss Francs, and euro, presently), drag-and-drop of auction URLs, a unique and powerful 'multisniping' feature, a relatively nice UI, and is known to work cleanly under Linux, Windows, Solaris, and MacOSX from the same binary.
What it does not say, is it is open source and one useful peice of software!
Other links: Developer Blog