Gateway MD7820u Laptop for $599.99 shipped.  This is a well-loaded laptop with 15.4" LCD, Core 2 Duo CPU at 2.0GHz, 4GB of DDR3 RAM, 320GB HD, Radeon HD 3650, DVD burner, built-in digital media reader, wireless-b/g/n, webcam, 6-cell battery, Vista 64-bit and more.  Note that it weighs about 6.5 lbs so this is perhaps more like a very portable desktop instead of a truly lightweight laptop.  Others sell it for about $749.