Had a call the other day from a client needed a laptop to use when travelling. After a chat we determined the main use would be email and spreadsheets. Nothing to graphics intensive and no games. It did have to be able to play DVD movies for those long flights.
There is quite a few ultra portable notebooks in the market. They offer very low weight, around 1.5 kgs and pack impressive processing power using new ULV ultra low voltage mobile chips.
Some models also come with built in 3G network modems giving great connectivity on the move.