Microsoft Source Analysis for C#
Source Analysis, also known as StyleCop, analyzes C# source code to enforce a set of best practice style and consistency rules. It can be run from inside of Visual Studio or integrated into an MSBuild project.
You can download it here.
For more information about Microsoft Source Analysis for C#, see the Source Analysis blog at http://blogs.msdn.com/sourceanalysis .
More resources can be found here.