The Microsoft F# research team recently released the September 2008 CTP of F#.

 

F# developed as a research programming language to provide the much sought-after combination of type safety, succinctness, performance, expresivity and scripting, with all the advantages of running on a high-quality, well-supported modern runtime system. This combination has been so successful that the language is now being transitioned towards a fully supported language on the .NET platform. Some of the reasons for this move are that F# gives you:

You can download it here.