JemJem offers the refurbished 2.4-lb. Apple MacBook Air Intel Ivy Bridge Core i5 1.7GHz 11.6" Laptop, model no. MD223LL/A, for $539 with free shipping. That's $60 under our refurb mention from last fall and the least expensive 12" MacBook Air we've ever seen. (It's also $421 under the best we could find for a new unit.) It features an Intel Core i5-3317U 1.7GHz Ivy Bridge dual-core processor, 11.6" 1366x768 LED-backlit LCD, 4GB RAM, 64GB SSD, Facetime camera, Thunderbolt, USB 3.0, 802.11n wireless, Bluetooth 4.0, and Mac OS X 10.7 Lion.
A 90-day JemJem warranty applies.