I call it PopDuino, based on a ATMega644.
Complete and fully functionall on a surface of 35x75mm and costs 10 Euro to build.
Could not imagine that it would be this simple to build your own Arduino version.
Off course it would not be possible without the bootloader from the Sanguino team.
And the best part is that i have 64K memory and 8 analog pins and 24 digital ones.
Missing is the FTDI chip, debug light and power input option other then usb but not really needed all times.
For some of you, nothing new to read here but i am amazed of the simple world of Arduino.
Check out the complete product at:http://www.sanguino.cc
And this is the easy schematic, edited and borrowed from Sanguino.cc