So i remember a thread a little bit ago about a guy making a small ITX case just big enough for the motherboard and a single low profile expansion slot (couldnt find it sorry). Anyhow i ran across this which looks pretty much identical except they use a 120mm fan vent on top. They even have an option to use a custom block/heatpipes to run a CPU passively with the heat dissipated against one of the side panels.
Dimensions: 219 x 96 x 222mm (W / H / D)
http://htpc.jp/b/b110.html
Dimensions: 219 x 96 x 222mm (W / H / D)
http://htpc.jp/b/b110.html