Right now I have a 3 year old macbook and a 6 month old lenovo thinkpad edge.
Anyways, if you think a windows PC is the way to go, I would get a toshiba satellite or a lenovo thinkpad. These are fairly heavy (~5lb). If you get a higher end model, it will last you four years. There's a back to school promo where if you spend >=699 on a laptop, you get a free xbox 360, which you can sell on ebay if you want.
Buy a PC and Get a Free Xbox 360
If you want a mac, I think you cannot go wrong with the Macbook pro. If you hold off until september/october, they are going to release a sandybridge i5 macbook air, which will be an ultraportable (~2.5lb) heavyweight (SSD, newest gen, low wattage processor). If you don't want to wait, you can get $100 at the app store in addition to student savings on the air.
Buy a mac, get $100 at app store
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