In reply to Lord of Starkness: If work are paying or you can get a student discount, may be worth looking at a macbook air 11 or 13" (I prefer the 13"). I'm not a massive apple fan due to their fanboys and pricing(I'd never buy the iMac, cant justify the iPad etc) but its light, fully operational with a big enough screen to do enough work from, full keyboard. Battery life lasts around 6-7 hours I find between work, movies etc.
However I have not played with any of the brand new Asus Ultrabooks. But should you be a 'Which' fan the apple comes out top.
I had a netbook before which I really liked the only downside was doing any work, I found the screen a bit too small and the keyboard too compact.
iPad may be what you need, if the screen is big enough for you to work from and you don't mind the touch keyboard.