F# is a functional programming language which runs on .NET. In addition to supporting functional programming constructs, it also has object programming capabilities. This hybrid of functional programming with object-oriented capabilities makes F# a pragmatic language for accomplishing any task.
If You're New to F#
If you're new to F#, begin with the Tour of F# to get an overview of the language and some of its programming concepts. If you're using Visual Studio, the Tutorial project template contains the same content.
If You're Experienced with F#
If you know your way around F#, or want to learn more about a specific language construct, see the Language Reference. It's a thorough guide of all F# language capabilities.
Additionally, the F# Core Library Reference is a great resource for learning about FSharp.Core, the core library which is a part of F#.
The F# Software Foundation
Although Microsoft is the primary developer of the F# language and its tooling, F# is also backed by an independent foundation, the F# Software Foundation (FSSF).
The mission of the F# Software Foundation is to promote, protect, and advance the F# programming language, and to support and facilitate the growth of a diverse and international community of F# programmers.
To learn more and get involved, check out fsharp.org.