The world is full of program-based tools, so try to think of something that might be of practical use to a student at your school, or maybe a professor, or maybe the average homeowner... or any other form of managerial functionality that might require some data management, catalogue elements, graphic presentation, etc.
I find it helps to be interested in the subject matter, think of something you like and go from there.
Flash is more than Banners, Sites and Animation, it's can be used for just about anything you can imagine.
Although it's best not to try and re-invent the wheel, somethings are just easier to do in other plaforms.
Hope it helps.