I know of two very early stage systems in ruby: https://github.com/jdleesmiller/rucas (which I wrote) and http://brainopia.github.com/symbolic/

I don't think either is really very useful at this stage (certainly mine isn't), but ruby does provide some very nice metaprogramming support for encoding and manipulating symbolic expressions.

Does your university not provide Mathematica? If not, I highly recommend purchasing Mathematica for students. I love open source software and particularly Python (yet I haven't tried Sage yet...), but Mathematica just strikes me as one of the "great pieces of software" with the likes of emacs, the Linux kernel, and etc.