Teamviewer is a small utility that allows you to take control over a computer anywhere on the Internet, even through firewalls. Actually is a vnc client that requires only port 80 (http) to work.(Edit: I' ve just heard about CrossLoop which looks like a free alternative to teamviewer)
Website: http://www.teamviewer.com/
License: Shareware
Similar programs: LogMeIn Hammachi (vpn over http), CrossLoop
