It's fun enough to learn to think with portals, but there's arguably little in existence that is more fun than learning with the Portal games as an educational tool. As long as you don't have to hear that damn song ever again. Because the people at Valve know this, just like they know the deepest secrets of our little consumer hearts, they are offering the first Portal for free on Steam -- until September 20th, that is.
If you want to learn more about their programme for using these games in education, check out their special website or watch the video above. Thanks Valve, even though I think everyone and their grandmother already owns Portal. If not, here's yet another chance to add it to your Steam collection for the grand total of nothing. (Psst, it works on a Mac too.)
[Also thanks to everyone who sent this in!]