This Team Fortress fan animation created with Source Filmmaker is a cool tribute to the ZombiU CG trailer.
Meet the Medic - Behind the Scenes
See outtakes and learn about Valve's creative process in this behind the scenes article for their Meet the Medic short.
Portal 2 - Boots
The science of the boots used in Portal 2 is explained in this latest video from Valve.
Portal 2 - Turret Trailer
Valve spills the beans on the technical aspects of the turrets encountered in Portal 2.