MegaMacs offers the refurbished Apple Mac Pro Intel Xenon 4-Core 2.66GHz Desktop PC (no monitor), model no. MA356LL/A, for $739.99 plus around $45 for shipping. That's the lowest total price we could find for a used one with the same configuration by $144 (this one's refurbished). It features dual Intel Xenon 2.55GHz Woodcrest dual-core processors (four cores total), 2GB RAM, 250GB hard drive, SuperDrive, NVIDIA GeForce 7300 GT 256MB graphics, and more. Deal ends March 7 at 1 pm ET.

Note: A 30-day MegaMacs warranty applies. Also, an OS is installed on this system, but it's unclear which OS it is.