Valve is up to it again, giving away some of their best titles for free. This time with TWP favorite Portal 1:

When we heard the buzz surrounding the new role video games are playing in education, we had to throw our hat in the ring. Today, innovative educators are finding ways to incorporate Portal and Portal 2 into their classrooms?helping teach physics and critical-thinking skills. It's eye-opening to see how video games can be used in amazing and unexpected ways to help educate our next generation.

Get it while you can, the offer only lasts until 9/20!

Learn With Portals free Portal 1 download