I would recommend an IBM laptop. One of the Centrino or Pentium M.
I have the T40. Its very thin, quite light (lighter than most). Durable, you can drop it/bash it and nothing happens. IBM screens are regarded by many as the best and brightest, I was impressed.
Also on a good day from a full charge I can get 7 hours out of the battery if the screen brightness is turned down and I'm just word processing or watching a film.
Only slight problem is the price. IBMs tend to be vastly more expensive than others but you are paying for the build quality. If you browse ebay a bit you can find some very good deals. I got the T40 for £700 a year ago, relativly brand new(box had been opened), when the RRP was still about £1600+
Generally speaking though, if you don't want an IBM then make sure you get a laptop with Centrino. Much longer battery life, very fast and very thin. Also intergrated wireless is good for those airport wireless hotspots.
PM