This got plugged on MacBreak Weekly (a great podcast looking at Mac issues) and it looks like it could be handy – Schoolhouse is a free (Mac-only) software program that will help you keep all your assignments lined up. You can keep all your notes together (including rich text format stuff), PDFs, other files, due dates and grades.
Looks pretty slick. Staying organized is one of the hardest things to do – this could help. I’m not sure how it can be used from the teaching side, but I’m going to start playing with it.