Steam

Steam.

Steam is VALVe's new automated content delivery system. It is a program you download that allows you to connect to VALVE's network and receive games (such as Counter-Strike), updates, and patches seamlessly.

Steam includes a number of features for making the way you play your games much easier:
» Automatic Updates
» Server Browser
» Friends System for Tracking and Communicating with Other Players
» Purchase and Download New Games

Homepage: http://www.steampowered.com
Support Center: http://support.steampowered.com/cgi-bin/steampowered.cfg/php/enduser/home.php