F# itself is an open source and cross-platform functional-first programming language, see fsharp.org for more details.
Microsoft contributed to both the design of the language and its primary implementation, and provide enterprise-level support for the language implementation and its tools through Visual Studio 2010, 2012 and 2013. Many staff within Microsoft Research continue to be active contributors to F#. for the latest version Microsoft staff contributed to the design of the F# 3.1 language, their implementation, advice to the Visual F# team, applied research contributions in the application of F# type providers, and work with the F# community.
If your interested in learning more about the enhancements in F#3.1 and the updates to the F# language and the Visual F# tools found in Visual Studio 2013 take a look What's New in Visual Studio 2013 here and in the Visual Studio F# Team Blog pre-release announcement.
If you’d like to know how F# is being used in practice, see the testimonials provided by the F# Software Foundation.
Even better, please contribute one of your own.