A lot of my smaller devices uses FreeRTOS, it's got a nice simple scheduler and it's easy to work with. I've also used the uEZ application later from FDI on to

A lot of my smaller devices uses FreeRTOS, it's got a nice simple scheduler and it's easy to work with. I've also used the uEZ application later from FDI on top of FreeRTOS when I need a more robust application. Although I'm looking at the Kinetis M3 line for upcoming work, so I might use mbed.