Another recent P2P release which I have been testing for the past month is called
Grouper.
It is distinct from the other programs in that it allows you to stream your audio content as well as make available your content for downloading.
The only stipulation with Grouper, is that you can't post Mp3 or WMA file extensions directly for downloading. However, most users either zip the files or my preference is to simply change the file extension of Mp3 to AVI. The AVI extension plays in Winamp or Windows Media Player. Naturally you can change the extension back to Mp3 with "Extension Changer" tool.
The biggest negative of this program? Big resource hog.
Give it a try here:
http://www.grouper.com/BTW: Another soon to be released option is called "AllPeers" connected through Mozilla. It will be out in a few weeks:
http://www.allpeers.com