Panasonic just released a new series (its 5th) of its "Let's Note" laptops in Japan, according to Akihabara News. I think some version of these may end up in the US at some point. In Japan they range from the 14.1" Y5, to the 12" W5 & T5, to the diminutive 10.4" R5. The Y5 weighs in at an incredible 1.5kg, lighter than my 12" G4 Powerbook, and sports a 1.5GHz IntelCore Duo. The T5 is just about 1kg and is powered by 1.06Gz Core Solo. These are tough machines, as the keyboards are waterproof and can take 100kg pressure. They also have a 7-9 hour battery life. The Panasonic Japan website has more stats, but in Japanese.
Apple's two MacBook Pros have faster processors (1.83-2.16Ghz), but are heavier (2.5 and 3.1kg) with bigger screens. The much rumored Intel iBook (or MacBook?) is thought to have a 13" screen, but I'm not sure we can count on Apple to make it light enough. Light laptops are in demand, especially in Japan.
Please, Apple, stop wasting time with giant laptops (like the 17" MBP) that are not really portable, and put some resources into making a laptop small enough to compete head-to-head with the myriad of small Windoze laptops on the market now. Even 2kg is too big!