OpenVPN
As a user-space VPN daemon, OpenVPN is compatible with with SSL/TLS, RSA Certificates and X509 PKI, NAT, DHCP, and TUN/TAP virtual devices.
OpenVPN is not compatible with IPSec, IKE, PPTP, or L2TP.
OpenVPN server setup on Slackware 13.37 - Multi-client with routing (not bridged). (2012)
OpenVPN server/client instructions (Pre-2009)
OpenVPN Instructions - Bahasa Indonesia (Pre-2009)