Think Thin
The lucky folks over at DesignTechnia have a review up of what may be the thinest laptop in the world - the Sony X505. It weighs in at just under two pounds (~910g) and is made of either nickel carbon or carbon fiber (your choice). The mini-laptop measures 10.07 x 8.19 inches (~256 x 208mm), and slopes from .38in (~10mm) thick in the front to .86in (~22mm) in the back. Yes, you read that right, at its widest it's less than an inch thick. Wow.
As with any extreme design, there are tradeoffs. A trackpoint replaces the usual touchpad, and it doesn't have an integrated DVD/CD drive, wireless LAN, or memory card slot. You can get external dongles to remedy these potential problems so you aren't completely left in the lurch but it is less convenient to use because of it.
The price for the grey market import is about $3,500 for the nickel carbon and call it $4,000 for the carbon fiber. As with all grey market items, there is no manufacturer's US warranty or support. But if you must have the absolute thinnest laptop, this may be the one to have. YMMV.