A while back, there was a topic about some guys that worked on Ableton making a DAW that allows more than one person to work on a project at the same time. I don't know how far along they are. Back then I had mentioned OhmStudio. Well, it opened to the public for mass beta, as I understand.
Basically, every change you make is uploaded to their servers, and downloaded automatically by others working on the same project. So you are literally working at the same time as someone else on whatever you'd like. ITS A GIANT COLLAB.I don't know too much about it, lol
It's free, and seems to be looking all right, if not a tad confusing, but that's cuz its new, right? Anyway, I haven't tried it too much, and I don't think you guys should pass up the opportunity to try it, so I'll just leave this here- http://www.ohmstudio.com
Here's a 10 minute video of some people using it in closed beta over a year ago.