moving on from python
If you just want to learn a new language you could take a look at scala. The language is influenced by languages like ruby, python and erlang, but is staticaly typed and runs on the JVM. The speed is comparable to Java. And you can use all the java libraries, plus reuse a lot of your python code through jython.
I use python heavily for manipulating data and then packaging it for statistical modeling (R through RPy2). 
Feeling a little restless, I would like to branch out into other languages where 

Faster than python
It's free
There's good books, documentations and tutorials
Very suitable for data manipulation
Lots of libraries for statistical modeling

Any recommendations?