There are some really interesting sets of programming exercises available online. Many of these get very difficult very quickly if you are new to programming, but they are really good to know about. It is good to know what kinds of problems you will be expected to solve if you pursue a career in programming, and it is good to have something specific to aim for.
- Project Euler
- Project Euler is a set of about 400 math-related programming exercises. It has been around for a while, and is quite enjoyable if you like playing with math. It gets hard quickly if you are not a mathematician, but that’s part of the fun. Once you solve a problem, you get access to a forum where you can see how everyone else has approached the problem. You can learn a lot by becoming active in the Project Euler community.
- Rosalind is similar to Project Euler, except the problems all focus on bioinformatics. If you are unfamiliar with that term, it is the use of computers to solve problems in biology. I just discovered this site, and it looks awesome!