Any open source language. If you are new to programming you can start with easy to learn language like Python. If you have programming experience then go for Clojure.

In open source world there are so many options, so it is better to keep learning rather than investing just in one language like people do in Proprietary world.

I don't see anything I really like a lot in python, and for clojure, is there a binary for windows?

Yes, you have binaries in windows for clojure on clojure.org - as clojure is written in java. You can also download clojurebox to have an environment to play with clojure (http://clojure.bighugh.com/).

Have fun!