I spend most my time doing Python (for scientific programming).
Knew Java, C++, Matlab and Perl before I learned Python.
A couple years ago, I learned R... I still use that a few times a week. Don't think it's improved my python programming.
More recently learned Clojure and Javascript. I think those count as meaningfully different from Python. I program differently in those languages, but I'm skeptical they've made me a better python progammer.