Discgolfscene.com is the answer. Not just for Michigan but anywhere. It started in Michigan (thanks Pete Crist) but has an active following for many areas and is increasingly popular.
Whether you are searching for courses, clubs, leagues or tournaments they are all easily available. The MDGO (Michigan Disc Golf Organization) used to publish a yearly tournament list. No longer as it is not needed.
Another cool thing is each player has a page which tracks league and tournament awards, aces and scores. I could never keep tracks of my aces from year to year without this (when you get old enough this will make perfect sense). Heck I'm not sure how many I have this year.