CowBoom offers the used Microsoft Xbox 360 250GB Slim Console for $69.99 plus $3.75 for shipping. That's $11 under our mention of a used unit from last month and the best price we've seen for this model. (It's $91 under the lowest total price we could find for a refurb.) It features a 250GB hard drive, 802.11n wireless, and HDMI.
Note: No warranty information is provided. This used unit may have dents or scratches and be missing parts or accessories.