Depends on which one you buy. Some (most) require that you put a bootloader in via STLink. There are, however, a few on EBay that sell them with the bootloader already burned in. They cost a buck or 2 more, but it's worth it. The one I'm using has a Maple Mini bootloader in it, which is supported by the Arduino IDE. Works great once you get your system set up with the correct hardware mapping files. BTW, these boards are advertised as having 64K memory, but every one I have works up to 128K.
See STM32Duino.com.
Joe
