A great tool released from valve that was in closed beta for a while that was used to make mini shorts using valves editor along with the engine source and is now open beta.Been messing around with it for a while my self and it indeed has a learning curve but if used properly,can be a great tool.
Quoted from Valve "Thanks for your patience, everybody! And a really big thanks to our first round of testers, who were instrumental in helping us make the SFM a better user experience.
They were SO helpful, in fact, that we're happy to announce that SFM Beta is now open to everyone, for free, as of right now. We've also provided a new SFM-specific page in the Steam Community where you can view, rate and discuss all the latest user-created videos.
Plus, just so we don't all overdose on "Meet The Heavy" shorts, we've decided to release a new session, to give all you folks something new to riff on. So get out your guitar (and some audio recording equipment) and prepare to "Meet The Engineer".
You can download the Source Filmmaker here on Steam."
Website Source of information : http://sourcefilmmaker.com/