...Ports are available for ARM, AVR, PPC, MSP430, 6502, MYCPU and for developing and testing purpose also for 8086, Win32 and Unix.
pico]OS 1.0.4 was released 2012-07-12. This is a maintenance release that includes some bug fixes for the new ports for MSP430 and ARM Cortex-M.
You may also visit Ari's website that contains cool stuff related to pico]OS: http://stonepile.fi/tags/picoos/