If the smallest available laptops are too big for you, you could try the new U60 from Gigabyte. Imagine a powerful laptop will full QWERTY keyboard, not much bigger than an average PDA.
Based on the VIA esther Mobile Tech, and VIA Esther ULV C7-M, this mini laptop can offer you up to four hours of autonomy. The screen is a 6,5 inch TFT wide screen LCD, with a resolution of 800x480 WXGA, powered with VIA VX-700 UniChrome PRO II graphics system.
The system basically comes with 512MB 533 Mhz DDR2 memory, and can be upgraded up to 768MB. For storage there is a 1.8 inch 4200 rpm IDE hard drive and it comes in capacities of 20, 30 or 40 GB.
Input-output system comprises of Media Card Slot (SD/SD-IO/MMC), two USB ports, audio jack, VGA, and a DC-in. External optical drives can be connected to the U60 via USB. For people in need of LAN connectivity, good news, LAN and WLAN hardware are integrated.
The laptop weights only 740g, which is really not much at all.