The Sanguino is an single board micro-controler very much inspired by the Arduino offerings and very popular as the basis for controling RepRap machinery.

http://sanguino.cc/

Patches are provided by the Sanguino folk to extend the Arduino IDE presenting the Sanguino as just another Arduino style board.

The Sanguino uses the Atmega 644P is available in a 40 Pin DIL package and offers 64K of memory plus more IO than the usual Arduino Boards, although it has recently been outshone by the Arduino Mega.