You might have seen this video already- I didn't see it till today and I think it is amazing! A Japanese band called Sour apparently selected the cast from amongst their fans and the whole thing was filmed solely by webcam.
In 'Director's Notes' you can hear a podcast of an interview with the four directors on how they made this!
It got me hunting for other collaborative videos and I stumbled across the result of a g-mail contest to make a video showing an e-mail travels around the world; this is a combination made from a range of the best entries:
There are more oddball collaborations around; I found this one which turns webcammers into a beatbox:
There are youtubers who devote their time to making them and then talking about them
And then there are seasonal collabs, so here's one to end on:
and this week's message?
MAKE YOUR OWN COLLABS!