ST launches four STM32 Nucleo boards with Arduino headers and mbed IDE. All $10.33 at Mouser. STM32F401RE at 84MHz Cortex-M4F. STM32L152RE at 32MHz Cortex-M3 (low power). STM32F103RB at 72MHz Cortex-M3. STM32F030R8 at 48MHz Cortex-M3.