Your first week in college is one of the craziest weeks of your life. You leave everything and everyone you have ever known, move out for the first time, and start living and interacting with hundreds of people on a daily basis. Move in week is full of emotions, so much more than just a little bit of sadness and a lot of excitement. You are overrun with fear about your new life, concern with what you're doing and where you're going, and are quickly forced to adjust to the calamity and chaos around you. Along with the million-and-one things you want and need to do to prepare for the semester is shopping -- lots and lots of shopping. For food, clothes, dorm decorations, school supplies. Everyone knows to buy binders and enough Ramen to fill your 10x15 dorm, but it is easy to forget those other things that don't seem essential at the time, but will make your life incredibly easier and better.
Rain boots and rain jacket
There is no such thing as buying rain gear 'too early' in the semester. It could just as well pour down on your FDOC as it could mid-semester, and you definitely don't want to walk into your first college lecture soaking wet. As soon as you can find rain stuff, you should get it. Most campuses also have rain jackets with their logos at the bookstore.
Air freshener
You know what smells worse than the stairwell of your building or your common room? The dorm room, when your roommate hasn't showered in two days and burns popcorn at midnight. Air freshener or plug in Wallflowers can work wonders in your small space.
Extra storage bins
Seriously, you can never have enough storage. Everything you bring into your dorm is going to be misplaced almost immediately, but you will be able to keep your life somewhat in order if you have a place for everything. And yes, even in college, you absolutely need a junk drawer.
Caffeine
Whether you yearn for coffee. Mountain Dew, or Monster, whatever your poison is, go buy it immediately. You have likely never been on the go as much or been as stressed out as you will be in the next few months, so it is best to prepare for it now. Stock up and be ready, classes are coming.
Portable charger
So it is the night before your first Bio test, you get to the library, sit down, and bam! your iPad dies. All of your notes and PowerPoints for the test are not accessible anywhere else, and now you can't do any more studying until you trek back to your dorm room and wait for it to charge. You have now lost half an hour of valuable study time, and it all could have been prevented by having a $20 charger.