Anakrino
Anakrino is a tool that decompiles DotNet assemblies into CsharpLanguage code. This can be useful for ReverseEngineering the under-documented .NET Framework libraries.

Asmex
Asmex is a viewer for the internals of .NET assembly files. While the world is not particularly short of .NET assembly viewers, Asmex has some unique features and the source might prove useful in various contexts.

F#: Assembly Explorer
F Sharp makes performing analysis on MSIL relatively easy, my biggest problem coming up with a sensible way to use this. The tool will show you the dependencies on a .NET .dll or executable. It will also draw a graph that shows all the function calls a method could make. I’m not sure if this will be really useful to anyway but I found it quite an interesting way to look at .NET code.

Reflector.FileDisassembler
The Reflector.FileDisassembler is a little add-in for the new version of Lutz Roeder's .NET Reflector that you can use to dump the decompiler output to files of any Reflector supported language (C#, VB.NET, Delphi). This is extremely useful if you are searching for a specific line of code as you can use VS.NET's "Find in Files" or want to convert a class from one language to another.