gostm32 is a single-topic blog about using an STM32Discovery development board with open-source dev tools.
The STM32Discovery is an absurdly inexpensive breadboard-compatible product bearing an STM32F100RB running at 24 MHz. It’s not the hottest Cortex-M3 chip on the block, but compared to SparkFun’s Cortex-M3 board or the LeafLabs Maple, which each use an STM32F103RB, this appears to be a very good deal indeed.