Honestly, different students like different things. You need to somehow narrow down your options. Do you want to do a graphics project? An AI project? A new feature for the empeg crowd to drool over? Do you want to add some feature to an e-mail or calendar client?

I could rattle off project ideas for pages and pages, but you first need to narrow down your interests. You also need to say something about how much time and energy you've got to spend on the problem. For some people, hacking Gnome Evolution to have decent shared calendar support is a weekend hack. For others, it's months of work.