JemJem offers the refurbished 2.4-lb. Apple MacBook Air Intel Core i5 1.7GHz 11.6" Laptop, model no. MD224LL/A, for $569 with free shipping. That's $10 under last fall's mention (which also included a Level 8 carrying case) and the lowest total price we've seen. (It's also the lowest total price we could find for a used one now by $11) It features an Intel Ivy Bridge Core i5-3317U 1.7GHz dual-core processor, 11.6" 1366x768 LED-backlit LCD, 4GB RAM, 128GB flash storage, 802.11n wireless, Bluetooth 4.0, Facetime camera, Thunderbolt, and Mac OS X 10.7 Lion.
A 90 day warranty applies, although it's unclear who supports it.