I have previously talked about Microsoft StyleCop. For those that might not know about it, StyleCop is a source analysis tool (different from the static analysis that FxCop performs) that analyzes the source code directly. As a result, it focuses on more design (or style) issues such as layout, readability and documentation.
In an interesting move (and one that I am happy to see), Microsoft has decided to make StyleCop an open source project (under the MS-PL license) available on CodePlex. (The project site isn’t up yet, but should be in the next few weeks.) This will give the development community the opportunity to help contribute to the project, expanding support to other languages (currently it only supports C#), adding features, and fixing bugs. Shortly after the CodePlex site is up, StyleCop 4.4 will be released which includes support for C# 4.0 as well as a large number of bug fixes and other improvements.