F#

"F# is a mature, open source, cross-platform, functional-first programming language. It empowers users and organizations to tackle complex computing problems with simple, maintainable and robust code."

Website | Source | Foundation | Official Docs (PDF)

Language Overview | Language Specification: 4.1 4.0 3.1 3.0 | Syntax Cheat Sheet: HTML PDF

Originally from Microsoft Research.

F# was originally a CLR-based variant of OCaml. Since F# 3.0, it has relaxed some of the direct compatibility with OCaml in favor of a friendlier syntax, but still very much holds to its roots.

Wikibook

Areas of use

Cloud: Cloud and SOA are places where F# has made some strong plays. | Azure functions | Fog for creating Azure apps

Web: There's a collection of different web frameworks for F#. Some are more recent than others.

Fable: A compiler powered by Babel designed to make F# a first-class citizen of the JavaScript ecosystem. See The Elmish Book for a practical guide on using Fable.
Sutil:
Using Sutil to develop a real world application
Suave

Mobile: Most of this centers around Xamarin; lots of the links on the F#.org site are old (2013-era).

Enterprise: Mostly links about why F# is good in enterprise development. A few nuggets of goodness mixed in. Domain Modeling and DDD in F#, Domain-Driven Design (DDD) With F# and EventStore.

Data access: Type providers are seriously powerful: Accessing loosely structured data from F# and C# XML, JSON, SQL. Agents and message queues: An Introduction To F# Agents | Agents