Microsoft has tapped Garrett Serack as their new Open Source Community Lead. In an attempt to move the company towards open source, Microsoft has charged him with "building and connecting Open Source Communities around Microsoft Platforms".
In the past Microsoft has had a rather antagonistic position in regards to open source. Points of contention include the business model, wherein Microsoft prefers to sell software while open source proponents sell services around the software. Another is the GPL, a type of open source license that is especially incompatible with closed source licenses.
Recently Microsoft has been experimenting heavily with open source in its developer line. Products under open source agreements include much of AJAX for ASP.NET, including the entire control library, IronPython, IronRuby, and the Dynamic Language Runtime.
Apparently Microsoft thinks these experiments have been successful, as they are now starting to push other products to be more open source friendly. Don't expect this to occur overnight however, as Microsoft is a large company with lots of independent teams.