Lambda the Ultimate

Cω (pronounced C-Omega) is an extention to C# in two areas: asynchronous concurrency (formerly known as Polyphonic C#) and XML data types (Xen). A preview compiler is now downloadable from MSR:

http://research.microsoft.com/research/downloads/

And here's a sample program.

I am not sure just how exciting this language is, but it has been a while since we discussed a DSL.

This project is very interesting: a CLR-based language with Python-esque syntax, optional type declarations, open compilation pipeline, and some interesting ideas about generators and class attributes. There are some unique ideas about running a dynamic language atop the CLR, as well, like syntax to declare "duck" typing for individual objects, which lets you use them as dynamic proxies for COM objects, web services, etc.

It's definitely a bit green, but if even a significant fraction of the features discussed in the "manifesto" are there, it looks like an impressive effort, regardless.