http://projecteuler.net/
Named after the great Mathematician “Leonhard Euler”, it’s a website to test your programming and Maths prowess. Of course I’d only recommend it if you do actually enjoy solving maths puzzles and enjoy programming, otherwise it might be just a little torturous!
Each puzzle has a single number which you can enter on the website as a solution. It will keep a record of all the solutions you’ve found and if you solve enough, your name will be immortalised on the high score board (Though there’s a lot of work to do to get there!). Once you’ve got the right answer you can see how other people worked it out too in various different programming languages. You will certainly learn a few new skills and probably improve your own programming along the way.
I’ll see you there.
Update: It’s also a great way to practice any new programming languages you may be learning. Check out the list of languages people have used.