AeroCool Zero Degree Flexi Case
 

"Viewing the case from the rear, it really looks like an upside-down ATX. This rear plate is interchangeable for either an ATX or BTX motherboard. Each side panel comes with two thumb screws for easy removal. This case gives you the choice of using either two 80mm fans or a single 120mm fan for rear exhaustion, and has a removable plate for mounting the PSU through the rear."

http://www.ocia.net/reviews/zerodegree/page1.shtml