CsUnit
- C# based unit testing framework for the .NET framework. Includes download, samples, tutorials and FAQ. [Open source, zlib/libpng license]
- http://www.csunit.org/

X-Unity
- A unit testing and integration environment for the Microsoft .NET Framework. Features include simplified unit test development, automated builds, Visual SourceSafe interoperability and e-mail notifications.
- http://x-unity.miik.com.ua/

Unite.NET
- Unit- and Integration testing for the .NET platform.
- http://www.ascentiv.ch/unitedotnet

NUnit
- A framework, based on the JUnit family, for building application unit tests. It assists with test-driven design, a technique of Extreme Programming. By Philip Craig.
- http://sourceforge.net/projects/nunit

.NETUnit
- An implementation of Kent Beck's XUnit testing framework designed specifically for unit testing components written for the .NET platform. [LGPL]
- http://sourceforge.net/projects/dotnetunit/