According to ChannelRegister, Microsoft's Dryad platform, currently in beta, works just like Google's proprietary MapReduce platform, but is meant for clusters running Windows HPC Server. Microsoft also has released the DryadLINQ programming language, which uses .NET's LINQ query language model.
There are some quirks, however. As the article notes:
The current version can't handle more than 2028 individual partitions. It's been tested on only 128 individual nodes. And the DryadLINQ LINQ provider can't yet handle all LINQ queries.