First suggestion: Python. Lot's of nice stuff for science (NumPy, SciPy), lots of other goodies, easy to learn, many people to ask or places to get help from. Plus you can explore data interactively ("Yes Wedesday, play with your data!").
Beyond that: CERN uses a lot of Java (sorry folks, true), they have good (and fast) tools I do a project right now where I am using Jython since it is supported by the main (Java) software I have to use. I like jhepwork/SCaVis quite a bit, if you are into plotting stuff on Java.
If you have extra free time and want to learn how to program well? I'd learn something like Smalltalk (for OOP concepts) and/or Haskell (functional programming). Scientists are often lousy programmers because they often do not learn programming properly, and/or the language allows them to get away with bad programming (I know, every language allows bad programmers to write bad code, but some make it easier than others).
So, stick with Python, it works really well, is modern, and has good support. Plus you can read your code in 5 years time
What do I program in? Python (and Jython), Perl, C, IDL (yickes!), Smalltalk, Matlab, Mathematica. I know some Lisp, but that's just for fun. And whatever allows me to load sketches on an Arduino. I like Python (get's stuff done) and Smalltalk (works actually like I think - passing messages between objects).
Use whatever works and you don't hate