WinMX is the 2nd biggest program...2 million users and 2 billion queues.
http://www.winmx.com/
Piolet is the former Blubster. Good general music program.
http://www.piolet.com/
GrabIt is a newsreader not p2p but with more content than IRC and requests filled often combined with maxing out your connection speed newsgroups are always at the top.
http://www.shemes.com/