1. IP
A. IPSec
FreeSWAN
CIPE
B. PPTP
PPTP Client
PopTop
C. L2TPD
L2TPD
3. Application
A. SSH
Surf at work
VPN Howto – SSH and PPP
B. SSL
SSL VPN
C. Others
Kaboodle
Links:
Google
VPN Labs
Linux VPN Client?
Intro to VPN – About
VPN Info
VPN – dtools
VPNC
FindVPN
VPN – CoreCom
Wikipedia