MINIX 3 Successfully Ported To ARM
MINIX 3.2.1 can successfully power-up on the BeagleBoard-xM with a working frame-buffer and is "off to discover the world." While there is a frame-buffer, networking support doesn't yet work on MINIX. MINIX 3.2.1 has been advertised as a great fit for ARM since its small, BSD licensed, and reliable.
Besides the BeagleBoard, the BeagleBone does work with MINIX 3 on ARM but there you get no working frame-buffer but do have networking support and USB support is forthcoming. MINIX 3 developers are planning to eventually support more Texas Instruments ARM hardware and the AllWinner ARM SoCs.
Those wishing to learn more about MINIX 3 on ARM can see the recent PDF slides here from the project's FOSDEM 2014 presentation announcing their working MINIX 3 ARM state.