One company that's making heavy use of F# is Credit Suisse. They use it in their global modeling and analysis group.

The F# based WebSharper web framework: http://websharper.com/. WebSharper is based on the work of Philip Wadler, et al: http://groups.inf.ed.ac.uk/links/formlets/

Here's another article by Philip Wadler on Formlets: http://homepages.inf.ed.ac.uk/wadler/papers/formlets-aplas/f...

Of course Microsoft uses F# for Bing data processing.