Pick something that interests you, something that you know at least a bit about, and hopefully that inspires a bit of passion. You really should try to find something that interests you rather than having someone else "dream up" an assignment for you.
For instance, if you are involved in the football team, see what software would help them. If you are interested in the theater, there are always things that they need to manage things (I know this from first hand experience, no amatuer / student theater group has nearly enough resources for custom software, but there is ALWAYS huge need). If you help out at a local homeless shelter, they need resources of any kind all the time.
In short, pick what interests you. You'll get more out of the project, and you'll actually help the folks that are most important to you.
-PatP