Dell Latitude, over here. I used to like Toshiba, and then bought a few Dell Inspirons before settling on the Latitude. (Yeah, we burned through a few laptops -- small companies will do that.)
Even though they're a notch more expensive (say, $1400 US rather than <$ 1000) the Latitude is worth it for me, since Dell commits to supporting each Latitude model for 10+ years. That means I can still buy batteries for my 5 year old D600 in the year 2010, theoretically. And all the Latitude parts & accessories are interchangable between Latitude models. For instance, in addition to my primary battery I have two spare batteries salvaged from defunct D500's.
None of this applies to the cheaper Inspiron. Dell buys whatever parts are cheapest at the moment to build those, and if you have to spring for a new power brick in a few years, you might end up on eBay or paying a premium price to Dell.
I agree with mouser on the basics: CPU speed and graphics performance are secondary on a laptop. If you want to play games you'd be better advised to spend your money elsewhere. However, I would make sure that you get a dual-core processor, since it makes a world of difference in how responsive the machine feels. Sure, your spreadsheets may longer to recalculate with a 1.5GHz processor, but you can still mouse around and read email while you wait.
I disagree that battery life is a non-issue. For me, the main criteria I use when selecting a machine is: can I last through a 6 hour flight on battery power alone? The Latitudes I've used are very good about this: with both primary & secondary batteries fully charged I get an honest 5.5 hours -- and that's on a 5 year old laptop with about a million miles on it. Swap batteries and I can go another 2.5 hours, easy. That's almost a transatlantic flight.
I paid $2100 for it back in 2002, so spread out over 5 years that's ~$400 per year. Not bad value for a machine that's been trouble free from day one.
And now that I've written about it, I've guaranteed it'll croak tomorrow! But that's no worry -- a new Latitude that'll kick this one's butt is around $1600, and I can still use my spare batteries.