HP and Toshiba are both great. I have an Apple laptop and have really loved it. If you do get an apple, then I definitely would not go with the macbook air. MacBook Pros are a little heavier, but they are the much better deal. It is mainly personal preference as far as which OS so I would say to choose whichever one that you like better.
Celegorm, how did you manage to get your college to provide you with a computer? That is soo lucky!!!! I have a hard time getting my school to even give me a student software discount.