.NET (dotNET) development


IronPhyton
Implementation of the Python programming language running on .NET
Microsoft Visual Studio Express
Free, lightweight, educational.
Mono
Develop and run .NET client/server applications on Linux, Solaris, Mac OS X, Windows, and Unix
RAIL
Runtime Assembly Instrumentation Library
Phalanger
The PHP Language Compiler for the .NET Framework
Ruby.NET
Gardens Point Ruby.NET compiler
PostSharp
Post-compiler: open platform for analysis and xformations of assemblies after compilation

.NET (dotNET) scripting


Alintex Script
Brings multi-language .NET and Java™† scripting to your desktop
C# Script
C#-Script execution engine version by Oleg Shilo
C# Script for .NET 2.0
Simple and powerful script engine for C# and .NET 2.0 (source project) by Ed Poore
DotNet Script Host
http://www.toolsack.com/products/dotnetscripthost/
DotNET Scripting Host (DSH)
Script host for the CLR and .NET Framework that simulates the Windows Script Host (WSH)
EezeeScript
A simple embeddable scripting language for .NET (source project)
Microsoft Research F#
Combination of type safety, performance and scripting
Snippet Compiler
As the name says, it compiles snippets

Language conversion and translation


Janett
Java to .NET translator

If you have a resource you think should be listed here, drop us a note.
This is not an exhaustive and comprehensive list but rather a place for us to share
interesting links and useful resources when we encounter them.