Sanguino
Sanguino is the Arduino’s Big Brother.Here is comparision Between Sanguino and Arduino
Similarities
They both use ATmega family chips, and are very similar in architecture. Knowledge gained from programming an Arduino is directly applicable to programming a Sanguino.
They both are intended to be programmed directly from the Arduino environment, so your sketches for Arduino will work with the Sanguino with minimal modifications.
They are both open source and 100% hackable.
They both use a bootloader for uploading sketches via serial.
Differences
The primary difference between the Arduino and the Sanguino is the processor: Arduino uses the atmega168, while the Sanguino uses the atmega644. The rest of the differences basically all derive from this.
   Sanguino
This is full detail on Sanguino website
sanguino.cc