STM32 is microprocessor created by STMicroelectronics and it is based on ARM Cortex-M3 core. It is good starting point for both entry level and advanced programmers in embedded systems. Boards and external debuggers are cheap. Some even include JTAG debuggers in device price – like STM32 Discovery or TI lm4f120 with Cortex-M4.
Here I will post some code I made for it.
Drivers for internal peripherals: