well, I just bought a laptop recently myself.
I'm going to heavily recommend against getting a mac, they're usualy 1 1/2 times the price for the equivalent pc.
on top of that, there's a lot of compatibility issues.
as far as requirements, I'd probably say
250-320 GB hard drive.
3-4 GB ram.
a dual or quad core processor(if it's a similar price, go for the quad, it's worth it)
beyond those, it's all preference.
I'm going to recommend you stay away from those real shiny, almost reflective finishes, they get dirty and attract fingerprints really easily.
as far as a good brand, my personal favorite is Toshiba, they've been really reliable in my experience, plus, if the laptop you like happens to still come with vista they'll send you a free copy of windows 7 until like january 15th.
a couple other brands to watch are gateway and, if you're careful, dell.
dell, if you're going to get one of those, try to make sure it's not one of their inspiron series, i've seen no end of problems with those.
good luck!