Half-Life: Raise the Bar is a fan-made short film inspired by the Half-Life franchise.
Valve's Source Filmmaker
Valve have announced the Source Filmmaker, their tool for creating animated films in a very intuitive way.
Portal 2 - Perpetual Testing Initiative
Valve are introducing the Perpetual Testing Initiative for Portal 2 with this new amusing trailer.
Portal 2 - Boots
The science of the boots used in Portal 2 is explained in this latest video from Valve.