Here is an urgent public service announcement for anyone who never played the original Portal. I don't care what your reasons were for skipping it. This is your opportunity to correct that great wrong: Valve, in its typically awesome fashion, is offering up the 2007 Orange Box companion/highlight as a free Steam download for Mac and PC users.
You'll need to act quickly, as the offer ends on September 20. That give you plenty of time to take advantage however, and you most definitely should if you've never played Portal. It's all part of Valve's "Learn with Portals" program, which encourages kids to build levels for the game. You can see what that's all about in the video above.
Source: Rock Paper Shotgun