Half-Life: Raise the Bar
Half-Life: Raise the Bar is a fan-made short film inspired by the Half-Life franchise.
Counter-Strike: Global Offensive - Trailer
Valve show a grittier more realistic use for Source Filmmaker with a trailer for Counter-Strike: Global Offensive.
Portal 2 - Boots
The science of the boots used in Portal 2 is explained in this latest video from Valve.