As you may have heard, Scott Guthrie announced today that they will be releasing the source for the .net framework and that you'll have debugging capabilities inside of VS 2008. You'll actually be able to step into the .net source and see what's going on. This is cool! I'm sure it'll also be a big boost for Mono: "Just how exactly are they writing that code?"
How much of the runtime will then be "borrowed" for open source projects?
Very good announcement.