Sygate Personal Firewall 5.6.2808 (Freeware)

Free for personal use, Sygate Personal Firewall provides best of breed security in a user friendly interface, protecting your PC from hackers, trojans and DoS attacks.

Features include full-ICS support, protocol driver level protection, enhanced logging, and more.

Sygate Personal Firewall delivers unobtrusive, highly configurable, enforceable rule-based security policy by constantly operating in the background of your PC. Policies regarding applications, trusted IP addresses, ports, protocols and scheduling can be customized to support and secure any network configurations or requirements. Designed with high performance in mind, it delivers top-notch security without sacrificing your computing power.

Note that from November 30th, 2005 all Sygate consumer firewall products have been discontinued but this versions is available here for free use.

PeerGuardian 2.0 Beta 6c (Open Source)

PeerGuardian 2 is Phoenix Labs' premier IP blocker for Windows. PeerGuardian 2 integrates support for multiple lists, list editing, automatic updates, and blocking all of IPv4 (TCP, UDP, ICMP, etc), making it the safest and easiest way to protect your privacy on P2P.

PeerGuardian 2 is Open Source, meaning the program code is available online for anyone who wants it. Not only does this allow you to make modifications or even branch off into your own project, but it encourages peer review of the code making sure any bugs are eliminated swiftly. Because PeerGuardian 2 is Open Source, you can rest assured there are no backdoors or spyware included.