STM32F103C8T6 - Blue Pill Development Board
STM32F103C8T6 Microcontroller board (aka Blue Pill STM32), with USB connector that can be used for USB device peripheral that is inbuilt in this controller. The board has Reset button along with SWD connector for programming and debugging. It has all the required voltage regulation circuitry and all the pins connected out to the 2.54mm pitch header. It's an ideal low cost version of STM32F1 based system to experiment with.
STM32F103C8T6 Datasheet [Redirect to ST.com]