FA has done a great job putting together calendars for people to upload that have Michigan team schedules, but I wanted to add this as well.
Google Calendars has calendars that you can subscribe to for all NBA, NHL, MLB, NFL, college football, college basketball, soccer, and even rugby.
Google is international, and as a result, they have international leagues included as well.
So if you want to make sure to properly follow Michigan football, Maccabi basketball, Dominican Winter Leauge Baseball, and Asia's World Cup qualifiers, you can.
Holy Crap Update: It also has scores updated in real time.