Open source STM32 MCU programming toolset
The Open On-Chip Debugger
IPDBG are free tools to debug intellectual properties (IP cores).
The GNU Toolchain for ADI's Blackfin and future processors
Superseded by http://www.ti.com/tool/msp430-gcc-opensource
Universal programmer/debugger. Universal embedded software framework.
An in-application debug probe for ARM Cortex-M microcontrollers.