First post, search wasn't helpful for this particular question.
I'm a college student and I just started going to class by bike (campus is only 4 miles away). For those who don't have a desk or locker or office or other place to stow personal items, what the heck do you do with your helmet? My backpack is already stuffed full with books and shoes, and it's horribly awkward/clumsy to strap it to the outside. I don't feel comfortable leaving it exposed to the elements hanging from the handlebars or saddle, even if I tie it into the lock somehow. Man up and leave it with the bike, or penny up and get a bigger bag?