.NET Reflector is a class browser and documentation viewer to easily view, navigate, search, decompile and analyze .NET assemblies in C# and IL.
Download here. Presentation here.
.NET Resourcer is an editor for .resources and .resx files used with the .NET platform. Resourcer allows editing of strings and merging of resource files.
Download and source here.
Writer is a simple editor for HTML files. Writer supports text layout and formatting, hyperlink editing and insertion of dates and pictures.