Here's a good article from Digital Web Magazine titled "Preparing For Widescreen," about the shift in laptops towards widescreen-format displays, and what that means for designing websites. -- via Airbag
The basic idea they're promoting is to build a site that is capable of going three-column for widescreen users, but dropping down to two (or even one) columns for narrower resolutions.
Having spent my lunch hour at the Apple store loading various sites on the 30-inch display, I can say that a little more planning for larger displays wouldn't hurt more sites. I can also say that using Google Maps on that large a monitor is awesome.