Newegg offers the refurbished Lenovo ThinkCentre M81 Intel Core i5 3.1GHz Desktop PC (no monitor), for $249.99 with free shipping. That's $150 off list and the lowest total price we could find. It features an Intel Core i5-2400 3.1GHz quad-core processor, 4GB RAM, 250GB hard drive, DVD drive, and Windows 7 Pro 64-bit.

A 90-day warranty applies, but it's unclear who backs it.

Update: The price has dropped to $244.99.