I used an STM32 for the first time in Robot2, and soon discovered how cool they were. Each one is packed full of neat peripherals, runs really really fast and can do all sorts of cool stuff that simpler µCs like an ATmega simply can't pull off. With this in mind, I asked ST for two samples of their STM32F103CBT6, a 48pin LQFP package. They sent the samples (thanks, ST!) and I got to making up a PCB to put them on.
I decided I wanted something with a lot of interface peripherals, so broke out USART1, 2 and 3, I²C1 and 2 (also USART3) and SPI1 and 2. Additionally a USB plug is connected to the USB peripheral, and JTAG is available. The 6pin header for USART1 is compatible with the FTDI cables/breakouts which makes interfacing with an FTDI cable for programming (the bootloader listens on USART1) or with an xbee on one of SparkFun's breakouts is very easy.
So far I've used one of these boards for Robot3 (an upcoming post) and plan to use the second to start prototypes with my quadcopter UAV. They're pretty useful, uploading code to them is quick and easy with the bootloader, and having that many peripherals available and capable of running at pretty high speeds makes these boards handy to have around.
Eagle files and a PNG here.