LL Bean, J Crew and Ralph Lauren will all allow you to fit in fine in Ann Arbor - although you'll definitely be on the preppy side.
LL Bean Maine Hunting Boots (the 8 inch ones) work quite well with khakis, jeans or sweats to get you through the snow and sludge.
A&F, American Eagle & Hollister are pretty typical options for college life as well. And don't knock the sweats/pajama pants and baseball hat look until you've actually been in the position of partying till 4:00 in the morning and still need to roll out of bed and make it to your 8:00 a.m. class but don't feel like showering.
20 years ago I headed from Arizona to Michigan for college with one jacket and several cotton sweaters. The first weekend that it got really cold I drove to Ann Arbor and stocked up on wool sweaters, gloves and a heavy winter coat. My parents never even really questioned me about that credit card bill
EDIT - you definitely need one of these. It's a crucial first piece for layering to see games in the Big House... add a heavy jacket, gloves, scarf and a thermos with hot chocolate and peppermint schnapps and you're all set.