SharpOS
MS Research has been working on a ".NET-based" operating system for some time. Its a pretty exiting idea that could open up all kinds of new possiblities. Now, it looks like the open source community may be getting in on the act. The mono-develop mailing list has been buzzing with discussions of a CIL-based OS. William Lahti has already start something he calls Jeto. Jeto is an open source managed OS based on GNU/Linux. If you want to stay up on the discussion or contribute...look at the SharpOS web site.