An object database written in C# for the .NET platform. Also exist Java version.

Free C# editor.

Provides C# wrapper for OpenGL and SDL along with some tools.

Free open-source plugin for Eclipse (itself a free and open-source development environment) with syntax highlighting, content assistant (intellisense for C# keywords), and ability to compile code from within the IDE.

A series of advanced collections and more than 50 generic algorithms that are designed to complement, not replace, the basic features found in the .NET Framework. [Commercial]

A standalone profiler for C# that measures execution frequencies for each statement while keeping the instrumentation of the source code to a minimum. [Open source, GPL]

A programmer's editor that supports color-coded syntax of the C# programming language. By C Point Pty Ltd.

Intel Labs C# implementation of portions of the CLI (Common Language Infrastructure) runtime library as defined in the draft ECMA CLI specification.

Provides C# source for tools written in the tradition of lex and yacc, redesigned in an object-oriented way. By Malcolm Crowe.

Convert VB.NET code to C# code at the project and code snippet levels. Description, sample screenshots, and ordering information. By Tangible Software Solutions Inc.