Use a laptop with Pentium M CPU (Score 3, Insightful)

For the x86 side, use laptops with Pentium M cpus for the battery/perf. The whole Centrino marketing thing is based on using this cpu with other intel hardware to maximize battery life. I have a x1000 compaq with 15.4" screen and it has lasted a little over 4 hours. I think it could have gone a bit more if I employed more power saving features. I even watched FOTR on battery. I had the dvd ripped to the HD so the dvd drive was not it use. I am not sure if it would have lasted with constantly spinning the disc. But basically if you really wants lots of battery life, use laptops with smaller screens (10" or 12") and keep 'em dimmed. Also minimize the use of the HD.

I also have iBook 12" and I have used it for over 5 hours on battery. I stopped using it after 5 hours so I am not sure how much more it would have gone for.