Mac OS X users and faithful readers of TUAW know that there is great power found in the command-line, but one of the greatest advantages of OS X's UNIX heritage is the secure shell (SSH) client and server. From the Apple Matters article on SSH tunnels for the common man: "SSH is a network protocol that provides secure communication between two computers." Its power comes from the ability to create an encrypted tunnel through which a client can send many types of internet traffic.
How to stream your iTunes library across the web for free – The Unofficial Apple Weblog (TUAW).