Linux VPN HOWTO
- Setting up a VPN with ssh and ppp.
- http://www.tldp.org/HOWTO/VPN-HOWTO/

OpenVPN
- SSL/TLS based user-space VPN. Supports Linux, Solaris, OpenBSD, FreeBSD, NetBSD, Mac OS X, and Windows 2000/XP.
- http://openvpn.net/

OpenVPN GUI
- A Windows GUI for OpenVPN. Gives a systray icon with a menu to control OpenVPN.
- http://openvpn.se/

Linux VPN Masquerade HOWTO
- How to configure masquerading of IPsec and PPTP VPN traffic.
- http://www.tldp.org/HOWTO/VPN-Masquerade-HOWTO.html

PPTP_GUI Home
- A graphical user interface to the pptp-client software for Linux & BSD.
- http://pptp-gui.sourceforge.net

Unofficial FreeS/WAN Site
- 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

tinc
- 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/

Tunnel Vision VPN
- Creates an encrypted Virtual Private Network, or VPN, between two Tunnel Vision-capable sites on the Internet. Authentication is made as secure as possible by sending encrypted passwords first-time, and never thereafter.
- http://open.nit.ca/tunnelv/

PPTP-linux client
- Linux, FreeBSD and NetBSD client for the proprietary Microsoft Point-to-Point Tunneling Protocol, PPTP.
- http://pptpclient.sourceforge.net/

Secure Forwarding of Services with SSH
- Contains ssh-ppp perl script to set up a VPN.
- http://csociety.ecn.purdue.edu/~sigos/projects/ssh/forwarding/

Linux-Sec: VPN Page
- Collection of Linux VPN HowTos and free software.
- http://www.linux-sec.net/VPN

Linux FreeS/WAN Project
- An opensource project and software package for creating IPsec VPNs to and from Linux machines.
- http://www.freeswan.org/

Linux IP Tunnel Mini-HOWTO
- Instructions on how to setup a IP tunnel under Linux
- http://linas.org/linux/iptunnel.html

OpenBSD - Secure Free Operating System
- 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/