This isn't the first time and not the most interesting of Microsoft forays into FOSS. Other than the mentioned contribution to the Linux Kernel, Microsoft has been for quite a few years supporting OSS projects through their BizSpark program. A program that allows open source projects to enroll in a 3 year full MSDN subscription for free and obtain lifetime keys to their products.
In a move that may cause shock, confusion, or no emotional change in the open source community, Microsoft has announced that today they’re opening a subsidiary called Microsoft Open Technologies. The new company will focus on open source projects, interoperability initiatives, as well as working with open source standards groups.