Portal: Survive! is a live-action short film based on the Portal game, and its tie-in comic Portal 2: Lab Rat.
Valve have announced they will release their Source 2 engine for free to content developers.
Valve's Source Filmmaker
Valve have announced the Source Filmmaker, their tool for creating animated films in a very intuitive way.
Portal 2 - Authoring Tools Open Beta
The universally acclaimed Portal 2 is getting a level editor. Valve has launched an open beta for the game's authoring tools.