Some details from HL2 world.
TF2's intergrated filmmaker. You can't really activate it now, but it's inside of the GCF. There's a publish to Steam token as well, which suggests some new Steam community features. Publishing Machinima directly to Steam for other community members to watch is a strong possibility. I imagine it will work with other Source games as well.
This also reminded of the
Steam Review find that Valve registered Steammovies.com, last May. Connect the dots.
Source filmmaker (Film editor that doesn't require Hammer)
http://i23.tinypic.com/15d8j81.jpg[/IMG]
It's probably what Valve used to make the TF2 shorts, so you can imagine the extent of control people are going to have over their Machinima or game movies. It's likely to come with the SDK, though it's not gauranteed immediately. It exists, and that's certain.