IPBlock: A PeerGuardian alternative for Linux
For those unfamiliar with IP blocking, here's the basic principal. When you browse the internet and download files, you have to go through thousands of different computers that make up the Internet. Various organizations set up monitoring software along the way to intercept your information. The most common reason to do this is policing online piracy.
This is where IPBlock comes in. Written in Java, it's pretty obvious what it's inspired by. It copies the interface of PG2, and does a great job of it. Just grab the correct package download for your distro, and you'll be shooting down spammers and government agencies in no time.