Sony just released what they claim to be the lightest notebook around - "based on 10" and above notebook class as of 09/2009. Configuration includes standard capacity battery and built-in mobile broadband module."
The X series laptop comes with a 11.1'' screen, supports a 1366 x 768 resolution, weighs 1.5 - 1.6 lbs. (with the standard battery), and measures 10.95" (W) x 0.55" (H) x 7.29" (D).
Besides that, it features:
2GHz Intel Atom Processor
533Mhz Front Side Bus Speed
up to 128GB Solid State Drive
2GB DDR2 SDRAM
Estimated Battery Life with Standard Battery (included, default settings: up to 3.5 hours, max. brightness: up to 2.5 hours)
Estimated Battery Life with Extended Battery (included, default Settings: up to 14 hours, max. brightness: up to 12 hours)
Power Requirements: 38 watts or less
Intel Graphics Media Accelerator 500
Intel System Controller Hub US15W Chipset
Intel High Definition Audio
Built-in MOTION EYE camera and microphone
Electro-Static touch pad
QWERTY keyboard, 82 kyes with 1.2mm stroke and 17mm pitch
Fast Ethernet (RJ-45) Protocol
WiFi Atheros 802.11b/g/n
Verizon Wireless Mobile Broadband Built-In
Integrated Stereo A2DP Bluetooth technology
Microsoft Windows 7 Home Premium 32bit
All this goodness can be yours, in case you're willing to spend at least $1,299.99 USD for the black standard edition with a 64 GB SSD or $1,499.99 USD for the gold signature edition with a 128 GB SSD.