The Daruino is an open hardware project aiming to build an Arduino pin-compatible board with a Arm-based CPU. The smallest board is based on the LPC1102 from NXP. This will bring around 50MIPS to a $5 package.
The standard board, EV01 is based around a Arm Cortex M0 with 128KB FLASH and 16KB RAM. Running at 50MHz, the PCB is the same size as the Atmel CPU used on the Arduino Uno boards. Remove the Atmel CPU, replace it with an EV01 board, and you’ve got something looking and working as an Arduino, but in a completely new performance range.
The idea here is not to interfere with the concept behind Arduino, instead to provide another option in the same spirit. Work is being made to support sketches on a code-compatibility level. Most shields will also work.