I can't promise OmniFocus will be worthwhile for your studies. Some people say it saved their grades, others definitely find it overkill. It's probably best for you to download the Mac app (2 week free trial at
www.omnigroup.com/products/omnifocus) and try it for yourself.
A number of students have posted on these forums before. Here are some of the threads discussing ideas about how to organize schoolwork:
http://forums.omnigroup.com/showthread.php?t=19978
http://forums.omnigroup.com/showthread.php?t=18379
http://forums.omnigroup.com/showthread.php?t=12639
http://forums.omnigroup.com/showthread.php?t=11052
http://forums.omnigroup.com/showthread.php?t=10732
http://forums.omnigroup.com/showthread.php?t=4345
(Some of them may be a bit out of date when describing specific menu items, etc. but the general principles should still apply.)
And feel free to post more specific questions as you get going with the app.