Valve have created Expiration Date, a 15 minute animated short featuring all the Team Fortress characters.
Portal: Survive! is a live-action short film based on the Portal game, and its tie-in comic Portal 2: Lab Rat.
When Gordon Met Chell
Portal joins forces with Half-Life in this short film called When Gordon Met Chell.
The first minutes of the original Half-Life are brought to life in this live action short, Half-Life: Origins.