Common Lisp and Smalltalk, especially Squeak, are my two most favorite languages. For the last couple of years, Alan Kay, David Reed, David A. Smith, and Andreas Raab have been toiling away on a major infrastructure built on top of Squeak called Croquet. It now looks like Croquet is very close to a major unveiling.
I've played with the alpha they had a couple of years ago and it's pretty amazing. It really could spark brand new ways of thinking about computing. This is the stuff you'd build The Matrix with.
The best way to learn about it is to watch Alan Kay demo it. He's done several demos of it, but I think the best demo was at Stanford last year.
Some references: academic papers, the original (2 year old) user's guide, and a pretty good introductary article.
After being amazed with the truly breathtaking OpenGL user interface, make sure you dig in deeper and find out about the architecture they have for supporting distributed collaborative objects.
This is going to be very important.