Shareaza is simply the best P2P app that I’ve found yet. It’s very small, and very stable. There are no annoying popup ads or spyware, nor do they try to coerce you into buying a commercial version (there isn’t one!) It’s totally free, and it just works great from the moment you install it. It’s very configurable, so you can optimize it for your particular system if you like. It runs on the Gnutella network, so the selection of files to download is slightly less than that of FastTrack/Kazaa, but IMO it more than makes up for it with its great features and stability that Kazaa lacks. Generally you can expect Shareaza’s frequent new version releases to have cutting-edge features that will take other P2P apps months to catch up to.