NHibernate is a port of Hibernate Core for Java to the .NET Framework. It handles persisting plain .NET objects to and from an underlying relational database. Given an XML description of your entities and relationships, NHibernate automatically generates SQL for loading and storing the objects. Optionally, you can describe your mapping metadata with attributes in your source code.
NUnit is a unit testing framework for all .NET languages on any .NET platform. It was ported from JUnit.
Mono provides the necessary software to develop and run .NET client and server applications on Linux, Solaris, Mac OS X, Windows, and Unix. Sponsored by Novell (http://www.novell.com), the Mono open source project has an active and enthusiastic contributing community and is positioned to become the leading choice for development of Linux applications.
log4net is a tool to help the programmer output log statements to a variety of output targets. log4net is a port of the excellent log4j framework to the .NET runtime.
Castle aspires to simplify the development of enterprise and web applications. Offering a set of tools (working together or independently) and integration with other open source projects, Castle helps you get more done with less code.
CruiseControl.NET is automated continuous integration server for the .NET platform. It is a C# port of CruiseControl for Java.
MonoDevelop is a GNOME IDE primarily designed for C# and other .NET
CruiseControl is a framework for a continuous build process. It includes, but is not limited to, plugins for email notification, Ant, and various source control tools. A Web interface is provided to view the details of the current and previous builds.
A fluent API for simplifying the entity mapping of NHibernate. Add compile time safety, testability, and improved readability to your NHibernate project. Cut down on some XML while you're at it too.
#develop (short for SharpDevelop) is a free IDE for C#, VB.NET and Boo projects on Microsoft's .NET platform.
MbUnit is an advanced xUnit framework. It is easily extensible and offers features that no other xUnit framework does. It has been described as NUnit on crack. One of the most important of it's unique features is parameterized unit tests.
Scala is a general purpose programming language designed to express common programming patterns in a concise, elegant, and type-safe way. It smoothly integrates features of object-oriented and functional languages. It is also fully interoperable with Java.
A wrist-friendly language targeting the Common Language Runtime (.NET / Mono) with an extensible compiler pipeline, a syntax reminiscent of Python, and many other features (like type inference, syntactic macros, etc.)
Cecil is a library written by Jb Evain (http://evain.net/blog/) to generate and inspect programs and libraries in the ECMA CIL format.
In simple English, with Cecil, you can load existing managed assemblies, browse all the contained types, modify them on the fly and save back to the disk the modified assembly.
Gendarme is a extensible rule-based tool to find problems in .NET applications and libraries. Gendarme inspects programs and libraries that contain code in ECMA CIL format (Mono and .NET) and looks for common problems with the code, problems that compiler do not typically check or have not historically checked.
Gendarme uses the Cecil library to introspect code.
OpenSimulator is a Second Life-compatible open source region simulator. Its companion project, OpenGridServices, provides the infrastructure for setting up a grid of simulators.
db4o is an object database available for Java and for .NET, including CompactFramework and Mono. Features include ACID transactions, automatic class schema recognition, Native Queries, query-by-example, S.O.D.A. object querying API, callback methods, memory files, cascade-on-delete and cascade-on-update. db4o runs in embedded local mode and in multi-transactional client/server mode.
NDoc is an extensible code documentation generation tool for .NET developers.
Second Life is a 3-D virtual world entirely built and owned by its residents. Since opening to the public in 2003, it has grown explosively and today is inhabited by a total of 6,642,422 people from around the globe.
Linden Lab is making the source code for the Second Life Viewer available to everyone. Talented developers from around the world will be able to collaborate with Linden Lab to refine and enhance the experience for all residents of Second Life.
Spring.NET is an application framework focused on helping build enterprise .NET applications. It provides a wide range of functionality such as Dependency Injection, Aspect Oriented Programming (AOP), data access abstractions, and ASP.NET integration. Based on the Spring Framework for Java, the core concepts and values found in Spring.Java have been applied to .NET.