Windows Development Environments

Visual C# 2010 Express is a free development environment for C#.

Visual Basic 2010 Express is a free development environment for Visual Basic.

Visual C++ 2010 Express is a free development environment for C++.

Microsoft Visual Studio 2010 Shell along with Microsoft F#, November 2010 Community Technology Preview provide a free development environment for F#.

Visual J# 2005 Express is a free development environment for J#, which offers the Java language syntax.

Non-Windows Development Environments (Linux, UNIX, Mac, and more!)

Mono is a free CLI implementation for most operating systems.

MonoDevelop is a free development environment for C#, Visual Basic, and C++.

This fsharp.zip download offers F# for Mono systems.