On the Windows side I am a big fan of IBM's laptops. They are very well built - super sturdy. They are, however, expensive. Next up would be Dell, who is fairly cheap but I've seen friend after friend go through hell trying to get stuff fixed by them. Finally, Sony's notebooks are also nice, but on the expensive side... they are very sexy, though.
Now, personally I took the plunge last year and bought an Apple Powerbook. It was my first Mac, and to be completely fair, I had hated Macs for a long time... but I gave in because of all the neat little features (such as a backlit keyboard). OS X is quite awesome... if it weren't for the fact I like games I would never buy a Windows machine again (as it is, I don't think i will buy a Windows laptop since I wouldn't game on a laptop anyway). Apple's are on the expensive side, although they do have a good student discount.