This is a tremendously exciting time to be thinking about programming languages and language research. I recently I have come across a lot of material that has made me think a lot.

Polyphonic C#

http://research.microsoft.com/%7Enick/polyphony/

            This is a C# like language that is built for concurrency control. Amazing piece of thought exercise there. I recommend looking at Modern Concurrency Abstraction for C#.

Xen/X# from Microsoft Research

Xen basically proposes to extend the C# language to better data handling support into the language. 

Unifying Tables Objects and Documents

This should give you a good idea of X#. This is by Erik Meijer of MSR.

Programming with Circles, Triangles and Rectangles

More – interesting reading.

C Omega

http://research.microsoft.com/Comega/

A combination of Xen and Polyphonic C#.

You might want to download this ppt that discusses C Omega by none other than Damian Watkins of MSR.

Groovy

http://groovy.codehaus.org/

            Groovy is the Ruby like language for the JVM. Ruby itself takes from the power of dynamic object oriented-ness that was so characteristic of smalltalk and whips a powerful expressive language on it. The thing is that Groovy also builds in Xen like concepts.

You might want to download this ppt that discusses Groovy by James Strachan co-author of groovy.

Self

http://research.sun.com/self/language.html

An old language from Sun Microsystems. Reading up about self makes you appreciate the spirit of many message passing and prototypes and cloning based pure object oriented systems.

I am not mentioning functional languages here because it is not fair to put up stuff I have no clue about. I must say this is an amazing time to be interested in programming languages.