Instant Replay Electronics via eBay offers the refurbished 4.5-lb. Apple MacBook Pro Intel Core i5 2.3GHz 13.3" Laptop, model no. MC700LL/A, for $529.99 with free shipping. That's $40 below our July mention and the lowest total price we've seen. (It's a current low for a refurb by $79.) Features include an Intel Core i5-2410M 2.3GHz Sandy Bridge dual-core processor, 13.3" 1280x800 LED-backlit LCD, 4GB RAM, 320GB hard drive, DVD burner, 802.11n wireless, Gigabit Ethernet, Bluetooth, Thunderbolt, media card reader, and Mac OS X 10.6 Snow Leopard.
Note: A 30-day warranty applies, although it's unclear who backs it.