I use a Toshiba U300-13U, its very portable with it's 13.3" WXGA screen. I bought it just over a year ago for around $1200. Its specs are:

Processor: Core2Duo T5250 1.5Ghz, 667Mhz Bus Speed with 2Mb L2 Cache.
Memory: 2Gb RAM, 160Gb HDD
OS: Vista Home Premium
Extras: Integrated 1.3MP webCam, Card Reader on the front, has a volume adjusting wheel on the side. Very small and light, weighing in @ 2.086Kg (4.6pounds).

Pretty basic equiptment here but all in the interest of getting a longer battery life, for working on the move.

I was getting around 2 hours out of the standard 4000 mAh battery, so got the 5200 mAh which boosted it to around 2.5-2.75 hours life.

Found a way to get around 10mins more out of the battery :) yey, simply by turning Vista's graphics to Basic, and disabling Transparency - closing the gadgets Sidebar is supposed to help also, but it's so beautiful I couldnt bring myself to close it.