dotPeek is a free .NET decompiler and assembly browser from JetBrains.

dotPeek allows opening assemblies right from the Windows Explorer by right-clicking on them and choosing Browse with JetBrains dotPeek. dotPeek decompiles any .NET assemblies and presents them as C# code.

Assemblies from Global Assembly Cache (GAC) can be opened via File | Open from GAC.

dotPeek provides a command that automatically decompiles the selected library and saves it as a complete Visual Sudio project. Right-click on the assembly in the Assembly Explorer, and choose Export to Project.

Source code that dotPeek decompiles is presented as C#. Code syntax is highlighted ReSharper-style, with distinctive colors for properties, types, accessors, and methods. When you put the caret on a delimiter, be it a brace or, say, parenthesis, it gets highlighted along with its counterpart, bringing focus to the scope of the particular code block you're in

Introducing JetBrains dotPeek Telerik - JustDecompile