I absolutely love my HP (Compaqs are the same thing these days)
I've yet to see a Dell laptop that weighs less than my desktop computer
Alienware's are made for gaming, not really the direction you are going in.
I would also look into Acer's, Toshiba, maybe the Panasonic Toughbook (I think thats pricey though, not sure). Sony's are as good as the next thing, but you will be paying more for the name. I'm sure there are other good brands out there that just aren't popping into my head right now, but I would definately suggest looking into an HP/Compaq first, and go from there.