The main thing about choosing programming languages to study is that there is no right answer. The best approach here is to suck it and see (if it sucks or not :-). There are plenty of sites on the net providing documentation and example programs - go take a look.

Two other considerations are:

What will the CompSci course be teaching or using?

This would be a good consideration. There are probably good reasons why they have chosen a particular language, as it may be good for introducing certain skills and algorithmic techniques. Also, you will steal a march on your classmates.

Which languages are popular on the job market?

This is less important at your stage, as your first job applications and resumés will not be able to count skills picked up in your own time - hobby programming. But, these skills come into fruition if you actually get to use a language or a technique on the job, if you have the understanding up-front.

In particular, there are a few languages not mentioned by others:

• Smalltalk

  This gives a very different, more dynamic feel of OO than C++, and Perl's OO is closer to this.

• Prolog

  Prolog will give you a good introduction to predicate calculus and AI.

• A pure functional language like SASL or Miranda.