Most schools reserve Macs for pre-publishing and photoshop classes. So unless you are focusing your education on those classes, I would not get a Mac. At my college, everything else was PC (WinXP), and even my Photoshop class had both PC and Mac workstations. I would focus on getting a system that meets the requirements of most of your classes. And for most colleges, they suggest a PC. Also check with your school to see what OS they use. Most still use Windows XP. Some are jumping up to Vista (or will be as soon as SP1 is released).
I would suggest a Dell Vostro 1400. They are smaller (14.1" widescreen), more durable than consumer notebooks (since they are business models), cheap (a well equipped system can be had for $800 or less), can be equipped with Windows XP or Vista Business through Dell Small Business (at least they were last time I checked), and can also be equipped with nVidia 8400M GS dedicated graphics (very nice to see in a 14.1").
Since you need a student laptop, I would suggest you stick with higher build quality models. That rules out just about every consumer notebook out there. Look for business class Asus's, Compaq's, Lenovo's, Dell's, etc... Something with a magnesium alloy chassis, spill proof keyboard, shock resistant hard drive, etc... You want a laptop that's a bit rugged that can handle being thrown into a backpack that doesn't get crushed with 3 or 4 textbooks in there with it. You don't need a Panasonic Toughbook- just get something that will last more than a year of rough handling and college abuse.
Another nice thing about the Vostro 1400 is you can equip it with a 2 year warranty for under $100. If you purchase with a credit card (depending on the card), you can get an extended 1-2 year warranty for free. So your 2 year peace of mind now becomes 3 or 4 years, enough to get you through most of your schooling.
And before you buy, head over to notebookreview.com, punch in the model, and look through the reviews. NBR publishes very detailed reviews (much better than cnet or the other big sites). The 1400 review is located here: Dell Vostro 1400 Review