NDoc generates class library documentation from .NET assemblies and the XML documentation files generated by the C# compiler. NDoc uses pluggable documenters to generate documentation in several different formats, including the MSDN-style HTML Help format (.chm), the Visual Studio .NET Help format (HTML Help 2), and MSDN-online style web pages. If you're new to NDoc, you can start with User's Guide. The Programmer's Reference also provides an example of NDoc's output. Here is the download page.