I say just don't worry about it. I ride to school (5mi uphill the entire way there) every day. I try to get there about 10 to 15 minutes before class starts in order to cool off and stop sweating. I don't change clothes, though I'm sure I sweat a lot. Be sure to wear a good deodorant/antiperspirant before you leave in the morning.

Also, I bring my bike in to class with me (I have yet to have a professor complain about there being a bike in the back of the class) so I don't have to worry about the bike thieves out there taking it off of the flimsy racks that are only held down by the bikes locked to it.

I ride clipless, so I have a trunk on my rack that I keep a pair of flip flops in when I'm riding, and my shoes in when I'm in class. Carbon soled shoes with Speedplay cleat = not fun to walk in.

Just my $.02