Some Mock Frameworks for use with .NET

NSubstitute
http://nsubstitute.github.com/

FakeItEasy
http://github.com/FakeItEasy/FakeItEasy


Moles
http://research.microsoft.com/en-us/projects/moles


Type Mock
http://www.typemock.com/

Simple.NET
http://simpledotnet.codeplex.com/