Just completed the submissions for Ann Arbor and Aspen. For these festivals I was able to use the phenomenally useful site WITHOUTABOX.
WITHOUTBOX lets you enter the information about your film once and submit electronically (everything but the film itself but that's coming) to each festival. If you're submitting to more than a couple of festivals, this is an incredible time saver. Not only that but the site provides a calender showing upcoming festival deadlines filtered by whether your film is eligible for the festival or not.
They have support for submission to hundreds of festivals (including some pretty big ones) and seem to be adding more all the time. They also have a larger database of known festivals that aren't part of the WITHOUTABOX submission system (yet) so you can still track their deadlines too.