Portal: Survive! is a live-action short film based on the Portal game, and its tie-in comic Portal 2: Lab Rat.
Half-Life Black Mesa
A relentless team of fans have finally released Black Mesa a remake/upgrade of the first Half-Life game from Valve.
Team Fortress 2 - Mann vs. Machine
A robot faction is introduced into the Team Fortress 2 equation, via this amazing new trailer by Valve.
Portal 2 - Boots
The science of the boots used in Portal 2 is explained in this latest video from Valve.