In short, it is a site where you should be able to find best practice code samples. You can even make a request for some sample that you need. Of course, not all requests will be granted but interesting and much sought code should appear there eventually.
Of course, anybody can upload their code sample for any request and thus take some load off poor Microsoft guy who got writing samples as a task. :)
It is interesting idea, but let's wait whether usefulness/noise will be better than rest of Internet.