I think I heard mention of this project during a recent episode of the FLOSS podcast a couple of weeks ago, and thought that it was an interesting idea, so remembered to track it down this morning. The basic idea is to provide a "loopback" device for video. You could write a program which can send out video frames, which are then read by any device that can read from v4l2 devices (like mplayer or mencoder). I have a couple of ideas for how this could be fun.
Sadly, typing "make" didn't have the desired effect on my "Jaunty Jackalope" machine, and looking back, it seems that it hasn't had an update since March 2008. It's probably a fairly minor thing. I'll try to work out the details later, and see if I can get it going.
Addendum: Some more playing around yielded some new links of interest. The
v4l2vd project mentioned the older vloopback, which is mostly unsupported, but which is apparently tagging along with the motion project, which does software motion detection on webcams (and notably v4l devices). You can find the software and such here, including a test application which accepts video from one device, and writes it back out to another.
I got onto this stuff by looking at the flashcam project, which I found while trying to find something like ustream that could run on Linux.
Dan Piponi passed along the following link to a nice paper summarizing the major results in number theory of the last decade or so. It's mostly over my head (Dan is substantially smarter than I) but pretty interesting nonetheless. [1010.2484] Progress in number theory in the years 1998-2009.