You need to specify your design requirements more. You would be best off with a Pentium M (Centrino) notebook for the thinnest case, best battery life and least heat possible but you have to specify the LCD size.

If you get a true ultralight (13.3" LCD or smaller) it will likely not be great for everyday use but these are ideal for traveling or if you want to plug in an external keyboard and/or external monitor. Many of these don't have dedicated video RAM (they have shared/integrated RAM) which is not ideal for games and/or intensive video applications.

A 14.1" LCD model would have the dedicated video, etc and would weigh in the 5.5 pound range

A 15.4" widescreen Pentium M notebook like the HPZT3000 series/Compaq X1000 series or the Toshiba M35 series or Dell 8600 is in the 6.2-6.9 pound range.

By specifying Sony and Fujitsu you may be specifying an ultralight model. Note that most Fujitsus under $2000 have only shared video memory even in the larger LCD sizes but at least 1-2 models over $2000 have dedicated video RAM.

Please be more specific for your LCD size and weight needs and whether you are willing to forego dedicated video RAM or not.

The Apple notebooks are lighter than their PC counterparts -- for example the Apple 17" Powerbook (about $2800) weighs only 6.9 pounds and that would weigh 9 pounds or over for an equivalent HP or Toshiba Pentium 4M notebook (there isn't a Pentium M Centrino notebook I am aware of with larger than a 15.4" widescreen LCD).