Soulseek is a Peer to Peer network that is mainly used to share music. It was launched in 2002 by a disgruntled former employee of Napster Nir Arbel who relies on donations from enthusiastic users of his service. As do other Peer to Peer networks, Soulseek has legal issues with copyright, but you need not worry, there are zero chances of the feds ever knocking on your door.
Whilst not the most used or well known of its kind, Soulseek has a fairly large user base and with patience just about anything can be found. There are some key differences between Soulseek and the Limewire/Gnutella brand of p2ps'.
1. Whereas Gnutella searches only a handful of users to find your search term, Soulseek finds every single file that matches your term of people online at the time.
2. Gnutella throws up a lot of junk and virus-ridden files, Soulseek never does.
3. Gnutella downloads from several users at once, whilst Soulseek downloads just from the users' file you have selected. This disadvantage can be mitigated by right-clicking search for the same file to ensure continuous download of your uploader leaves.
Of those three key differences the first two are obviously advantageous whilst the latter is a minus. Other features of Soulseek include: the ability to establish a wish list, so people you befriend can send you those files; the ability to ban people; superior conversation opportunities; ability to prioritise uploads to friends. You can also limit download/upload speed according to your wishes. One final minus is that you can only download one file per user at any one time, 'queuing' the others.
If you are considering using Soulseek. I wholeheartedly recommend it. It may be slightly slower but it is considerably lighter on your system, even with multiple uploads/downloads. It is the one Network you will be able to forget is on in terms of computer speed, and it is also charming in a quaint kind of way.
Soulseek(tm) is a unique ad-free, spyware free, and just plain free file sharing application.