Simplecortex is a microcontroller development board that is SHIELD compatible with the Arduino. The Simplecortex has a fast microcontroller, the LPC1769 from NXP. This is an ARM Cortex M3 microcontroller with 512KB flash, 64KB RAM and it runs at 120Mhz.
To make sure that the Simplecortex is easy to use, brc-electronics made tutorials for almost every periphceral on the chip and examples to get you starting. There are tutorials for simple stuff like IO control up to more advanced tutorials for MicroSD cards.
The Simplecortex also has an onboard debugger. It can also be used to program external devices like a self made PCB for your own project. No more microcontrollers with pre-programmed bootloader needed.
Simplecortex VS Arduino