OpenBSD aims to produce a free, secure multi-platform operating system that integrates strong cryptography including a current and complete IPSec implementation. http://www.OpenBSD.org/
Home of Super FreeS/WAN, ZeeS/WAN and FreeS/WAN + X.509 packages, as well as interoperability documentation and patches for additional features and broader compatibility. http://www.freeswan.ca
A self-contained VPN solution designed to connect multiple sites together in a secure way. Runs on Linux, FreeBSD, OpenBSD, NetBSD, MacOS/X, Solaris, Windows 2000 and XP. http://www.tinc-vpn.org/