Just to make it official: Our old home phoenixlabs.org is not active any more. So the only official place is here at sourceforge now: http://sourceforge.net/projects/peerguardian/
We are working on enabling and reworking more features here. Participation in any form is always welcome. This is an open project working on free and open source. Just use the Trackers and Forums here to get in contact.
PeerGuardian is a privacy oriented firewall application. It blocks connections to and from hosts specified in huge blocklists (thousands or millions of IP ranges). Its origins lie in targeting aggressive IPs while you use P2P.