Make a perpetual calendar with magnetic numbers that can be moved each month. The magnetic numbers can be put on any metal surface but why not put them on a decorated food can and have a multi use pen holder?
I am aware that this is a similar idea to www.instructables.com/id/Keylendar/
The ideas for my instructable were completely formed before I checked to see what was already on Instructables. I think my idea if different enough to warrant a new instructable.