Nothing can go on top of my AV receiver because it gets so hot and needs the space above it to breathe. The same is pretty much true of the XBox 360. But, given that the XBox is smaller its easier to make a stand for it to hold something above it.
Funnily enough, no-one makes an XBox 360 stand which covers the box when its lying horizontally and allows you to put something on top without covering the air vents...Oh well, i suppose I'll just have to make my own.
I designed this simple mini stand in Sketchup, exported it to an SVG file, then had it laser cut by Ponoko. The legs are shaped like controllers, but the scale is reduced down to about 90% so the stand is just tall and wide enough to clear the top and sides of the XBox. This lets air circulate through the vents in the box AND you can put other AV equipment on top if you need to. Sorted!
Here are direct links to the design files in github:
All the source is available in my Accessories repo on GitHub