show me the smallest case you know of

I know BTX may be around the corner but i'm interested in making a super small functional PC.

I saw a guy who did this hear, he had this little cube...very cool.

Anyways show me what you can.

The smallest PC I know of is the PSU PC which has a complete working PC inside a ATX-PSU.

The smallest mass produced form factor at this time in Mini-ITX however this is due to having everything onboard such as graphics, usb, firewire and processor. The ITX platform is 170mm x 170mm square.
I run a LARGE number of these systems and find that they suit my purposes excptionally well due to the low heat output they have, I have even run them withough the heatsink for a period of time (not suggesting that its a wise thing to do however)
The biggest problem however is that the consumer has unrealistic expectations of the form factor.
In general the form factor has low power and the Via-C3 100 mhz processor generally performs around the 500-ish Celeron performance mark and lower according to some benchmarks.. As such these things make fantastic file servers, firewalls, and little linux box's for web surfing and office work.
WindowsXP, Games and bloated applications however run like a dog with three legs.

The slightly larger SFF (Small Form factor) based systems such as the Shuttle Cube Systems (BigRed has his system in Front Page Discussions) and the Mini-ATX and Flex-ATX perform a great deal better than the ITX platform and often ship with luxurys such as AGP ports
Some PSU's for these systems do not provide and great deal of power and as such a hungry graphics card can affect the voltages.

Basically consider small systems as being a substitute and not a replacement for a full system

Shuttle is supposed to come out with a better 250w PS soon. Big Red still was able to overclock with a fairly power hungry 9800pro even with only a 200w PS. Once Shuttle gets that new PS, I'll be very interested in getting that canterwood model that Big Red has.

http://www.overclockers.com/articles773/index04.asp