Simple and functional P2P client compatible with iTunes
Cabos is a stripped down lightweight peer-to-peer file sharing application based on Limewire, which uses the Gnutella network (currently the 3rd biggest).
Cabos' interface will be instantly recognizable to anyone who's used Limewire before - you have your networks, downloads and uploads easy accessible on the left sidebar, above which sits the search bar and your current searches. The retouched Cabos interfaced looks simple yet modern, certainly an improvement over the aging appearance of earlier versions.
The results window allows you to order them by file type, artist, album, bitrate and so on. This 0.8.2 Cabos release features a nice new filtering system, that as well as filtering file types allows you to filter by keyword within your results, and four slides to further filter by size, bitrate speed and number of sources. This makes trawling through the sometimes odd results found in P2P searches much easier.
The Gnutella network is big enough that most people will be able to find anything they want in it, and while it may not be the fastest way to download, it's fast enough. Limewire and the other big P2P programs are more advanced, but Cabos has the advantage of speed. Compared to most programs like this it loads much faster, and is less of a draw on your processor, so your other applications shouldn't grind to a halt. That it's totally free and features no adverts or requests to 'go pro' make it even more attractive.
Cabos is a highly recommendable lightweight P2P client.