NUnit is a unit-testing framework for all .Net languages. Initially ported from JUnit, the current version, 2.2 is the third major release of this xUnit based unit testing tool for Microsoft .NET. It is written entirely in C# and has been completely redesigned to take advantage of many .NET language features, for example custom attributes and other reflection related capabilities. NUnit brings xUnit to all .NET languages. NUnit 2.2 Released The final release of NUnit 2.2 is now available from our downloads page.
NDoc generates class library documentation from .NET assemblies and the XML documentation files generated by the C# compiler. NDoc uses pluggable documenters to generate documentation in several different formats, including the MSDN-style HTML Help format (.chm), the Visual Studio .NET Help format (HTML Help 2), and MSDN-online style web pages. If you're new to NDoc, you can start with User's Guide. The Programmer's Reference also provides an example of NDoc's output. Here is the download page.
Firebird SQL is a powerful open source database that can be easily used in .NET. I believe it has a big potential (it is full-featured, requires zero administration, can be embedded, etc.). However this potential has not been fully discovered by .NET developers who rely on Microsoft SQL Server heavily. Download the Firebird Server, Embedded Firebird and ADO.NET Provider. Firebird Project's official home page.
A dynamic approach towards AOP on .NET is implemented as a library called Rapier-LOOM.NET. With Rapier-LOOM.NET, aspect weaving happens during runtime. This works because the weaver is being used to create (an interweave) objects instead of the CLI new operator. This version is very stable and can be downloaded in our download section.