If you use iCal (...and if yer a Mac OS X user, why wouldn't you?!) this website is really cool thing. There are a bunch of calendars that people have created tracking all sorts of different things.
Among the 782 calendars on the site currently: Academy of Art College Schedule, Enterprise, NYSE Market holiday and closings schedule and jusst about every sports schedule I can imagine. It's all neatly categorized and easy to sort through. Neat resource.