If you are interested in downloading individual games, you can do so by following the links on the games page.
If you want to download all of the games, you have several choices of files to download.
Originally the downloads were available via BitTorrent, though the BitTorrent tracker is no longer available.
In years past, the competition games and interpreters have been available from the IF Archive and other mirrors, putting a strain on those archives. To ease download requirements, we offered the files via BitTorrent, a peer-to-peer application that lets you download the files from other downloaders rather than from one central repository. If you would like to learn more about BitTorrent, the Wikipedia article about BitTorrent is a good place to start.
To use BitTorrent, you will first need to install a client. There are a lot of different clients available. While there are various heated opinions about which is best, for general use I recommend Azureus, a Java-based client. If you are allergic to Java and must have a native client, for Windows BitComet is a reasonable choice; for Mac OS X, there's Tomato Torrent.
This year's organizer is Stephen Granade.