I'm going to second the 13" Macbook Pro. I lived with a white Macbook for a couple of years, and while it was a brilliant notebook, the Macbook Pro 13" is even more brilliant. I just upgraded mine to 4GB of RAM and that went quite smoothly. The screen on the Macbook Pro 13" is outstanding, and having firewire for my external drive is a boon as well. Also believe it or not the backlit keyboard is awesome even if I only look at it and not use it in my dimly lit office (external keyboard I don't usually look at when typing in said room.)
Also the internal keyboard is a little better and the aluminum casing is just that much better. The trackpad is such that I use it often in lieu of a mouse. It is totally worth the extra centi-bucks to go with the Macbook Pro in that size. You get all the portability, the fantastic screen, and the extra perks that are over the plastic Macbook white. Not to say that the Macbook in plastic guise isn't a great notebook, it is. It's just that the Macbook Pro in the same form factor is a much greater one for the money.
Get the basic Macbook Pro 13" with 160GB HDD for $1200, then later upgrade the RAM to 4GB. This only cost me $77 from Crucial and was easy to do. Makes a world of difference and makes it the perfect small factor Macbook (that does Windows too) for minimum outlay of cash. Also the Macbook Pro is way sexy. Nothing wrong with that.