Honestly get a Macbook Air. I'm using mine from a tent while on touring right now

They are light, made of aluminum, I'd say pretty sealed from the environmental hazards (water...), crazy fast for a laptop (10 seconds to open Photoshop CS5 RAW Editor from idle?) and rather a nice screen compared to anything else. Nice big SSD hard drives too (64, 128 or 256 GB) compared to other options on the market.

Negatives? The charger is crappy. I killed my first one with little more than a splash of water (1 month old) and they can be funny at times with not wanting to charge at at. And they are not cheap to replace. Battery life isn't as great as they are hyped up to be, but they still can last for a good few hours and don't take that long to charge (about 4 hours run time surfing the internet charging my phone/ 1 hour 41 minutes to charge completely from dead)

MBA really could use a SIM card slot for internet access like some of the iPads.