Using thinner and richer designs of laptops is a present trend. Here is a list of seven thin and slim laptops that weigh less than 3 lb.
Fujistu LifeBook U 810 Mini NoteBook

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Price: $1,299
Weight: 1.56 lbs
Thickness: 0.76 inches
Features: Intel A110, 1GB DDR2 SDRAM, 5.6 in TFT active matrix. According to Company, batteries work continuously for 5.5 hours on a single charge.
Intel Mobile Metro

Image credit: cheaplaptops.org.uk
Price: $2,000
Weight: 2.25lb
Thickness: 0.7 inches
Features: Intel Core 2 Duo processor, Wi-Fi, WiMax and Bluetooth are some interesting features. It has a flash memory hard drive, with an expected battery life of 14 hours. This company offers a beautiful bag to keep this laptop with which you can wear this like a handbag.
Toshiba Portege R200

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Price: $2,999
Weight: 2.4 lbs
Thickness: 0.7 inches
Features: Intel Pentium M, 12.1 in TFT active matrix and offers an optical drive that has 128 GB worth of storage. The battery works more than 5 hours continuously.
Lenovo IdeaPad U110

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Price: $1,899
Weight: 2.4 lbs
Thickness: 0.72 to 0.88
Features: Intel Core 2 Duo, 2 GB DDR2 SDRAM, 11.1 in TFT active matrix. The battery provides up to 6 hours of battery life.
Sony VGN-TZ2000

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Price: $1,699.98
Weight: 2.7 lbs
Thickness: 0.9 inches
Features: Intel Core 2 Duo processor and 1GB memory. It offers hard drives in capacities up to 120 GB. The battery provides up to 6 hours of battery life.
LenovoThinkPad X300

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Price: $2,664 and up
Weight: 2.93lbs
Thickness: 0.73 inches
Features: 64 GB Hard Drive, 13.3 inch LED backlit display and lithium-polymer battery to provide better battery life up to 5 hours. It has three USB ports and a DVD Writer.
Apple Mac Book Air

Image credit: Apple.com
Price: $1,799 and up
Weight: 3lbs
Thickness: 0.16 at the thinnest and 0.76 at the thickest
Features: Intel Core 2 Duo processor, 2 GB DDR2 SDRAM, 13.3 in TFT active matrix and a built-in iSight camera are some of the features. The 37-watt-hou lithium-polymer battery provides up to 5 hours of battery life.