Fiddler

Fiddler Web Debugger - A free web debugging tool:

"Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP(S) traffic, set breakpoints, and 'fiddle' with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language."

moq

moq - Google Code: "The simplest mocking library for .NET 3.5 with deep C# 3.0 integration"