ARM Cortex (M3-M4): manufacturer and development IDE
A platform that has free compiler/IDE comes to mind:


mBed platform. It's based on a Cortex-M3 microcontrollers: NXP LPC1768. It has an online compiler/IDE. Programming language: C/C++


As a downside, the microcontroller has a preprogrammed bootloader which takes up some space in the program memmory. On the other side, you don't have to spend additional money to buy a programmer.