Microsoft Research has a number of very interesting programming languages currently baking in the oven. I find most of them extremely interesting, and will probably be babbling on about some of them in the coming weeks. Here’s a quick breakdown of what appears to be available:

AsmL: Stands for the Abstract State Machine Language, and is an “executable specification language.” It was designed to assist the engineering process, and to allow people to write executable, verifiable design blueprints through the use of abstract state machines. This one is a CLI language, and sounds like it integrates nicely with the rest of the Framework.

Cw: X#, then Xen, and now Cw (C-Omega). Based on C#, but extends it in some particularly cool ways. It enables first class support for XML and data manipulation. The core concept is discussed in good detail within a number of very well known essays (Programming with Rectangles, Triangles, and Circles, and Unifying Tables, Objects, and Documents [PDF]). A managed language.

F#: A great mixed language (functional and imperative) based on ML and Caml. This one is also CLI-based, and as such one of its primary goals was to function nicely with the rest of the Framework. That said, it implements many of the OCaml libraries so it remains autonomous if that’s what you’re looking for.

Pan: An odd little one. A Haskell-based functional language, whose primary goal is to enable image manipulation and pretty nifty graphical effects. Looks like a fun language (and would be even better if it was implemented against Avalon!). It ships with its own interpreter, so it’s definitely not CLI-based.

Vault: A C-like grammar which adds to the classic language some syntactic sugar and many managed-code-ish features. It also uses the notion of API interfaces which, in addition to defining logical groupings of functionality, supports some contract-driven features. For example, compile-enforced pre-conditions are a core language facet. While it isn’t a CLI language, it still looks to be scrumbibilyunctious.