stm8flash, the free command-line utility for the STM8 and ST-Link, ST-Link/v2 has seen quite some improvements lately. In particular:
* All current STM8 devices (including the new STM8S001) are now supported.
* The full flash range is now supported (instead of just the lower 32K).
stm8flash was written by Valentin Dudouyt; many other people (including me) have contributed. stm8flash is part of the free toolchain for STM8 development. There are tutorials for STM8 development using free tools including stm8flash.
stm8flash works on various OSes, including GNU/Linux, MacOS, FreeBSD and Windows.