clojure

hlship's cascade - and a somewhat more expanded framework with some nice features but still very compact code.

macourtney's Conjure - oh dear, yet another framework for Clojure. This time one that is similar to Rails. Nice detail: comes with H2 as a pre-configured and included database - H2 is a database in Java, similar to SQLite, small, fast, lean. But can also use other databases.

weavejester's compojure - Pico web framework for Clojure. Comparable to Step for Scala or web.py for Python. Just the absolutely minimal necessary to put together a small web application.

rosado's clj-processing - how to marry Processing and Clojure. With this, you should actually be able to rebuild the Processing GUI on the Mac so that Clojure is used instead of Java. Perhaps not entirely uninteresting to play around with.

Clojure - interesting Lisp dialect that compiles directly to Java bytecode and integrates well with Java, but is conceptually more aligned with Erlang's ideas (no object orientation of its own, but a functional model as the basis, strong focus on parallelism) and makes extensive use of concepts from Common Lisp (macros, multimethods). Sounds very interesting.