Groupon offers the refurbished 5.5-lb. Lenovo ThinkPad T520 Intel Sandy Bridge Core i5 2.5GHz 15.6" Laptop, model no. 4242-R18, for $389.99 with free shipping. That's $409 off and the lowest total price we could find. Features include an Intel Core i5-2520M 2.5GHz Sandy Bridge dual-core processor, 15.6" 1366x768 LED-backlit LCD, 8GB RAM, 128GB SSD, DVD burner, 802.11n wireless, Bluetooth, fingerprint scanner, media card reader, and Windows 7 Professional 64-bit.
A 90-day warranty applies, but it's unclear who backs it.