Buying laptop for college, suggestions?

Title pretty much says it all. I'm off to my freshman year at UC Berkeley this fall, and I'm going to buy a laptop. Well, I'm still a bit conflicted as to whether I want to buy a laptop or build a pc, but that's another story. Anywho, as I'm paying for the laptop myself, I need to say on budget. However, I need a laptop that will last me (specs and quality wise) for at least 4 years, have a pretty good battery life, not so heavy as to prevent me from carrying it from class to class as necessary, and not be too "middle of the road" if possible. As I'm sure many of you have been in my position before, your input would be greatly appreciated.

And for your troubles, a nice chauvinist joke (I kid the feminists, honestly):

What's worse than a despisable chauvinist pig?

A woman who won't do as she's told!

 

What's the budget?