Processing
As usual, Glen is ahead of everyone on this, but yesterday I got an overview of the Processing environment from the guys who wrote it, and it's so freaking HAWT. It runs on the JVM, but it fixes most of the annoying issues of "where's that jar file?" and "why do I need a class for the main loop?" by constraining the environment to a specific problem domain. And the results are both literally and figuratively beautiful. It feels to me like the kind of think that the Chumby guys should have been using instead of Flash.