I have posted a port of FreeRTOS here Google Code Archive - Long-term storage for Google Code Project Hosting.. The file is FreeRTOS20111031.zip.
There is also a port of ChibiOS/RT posted as ChibiOS20111027.zip. See http://arduino.cc/forum/index.php/topic,76932.0.html.
I have attempted to use the same options in both ports.
I used timer 0 for the system timer so the OS tick time is 1024 usec or 976 Hz.
I provided the same five examples in each port.
There are five examples in the FreeRTOS/examples folder.
frBlinkPrint - A simple example of three threads. A high priority thread
blinks an LED, a medium priority thread prints a counter
every second, and the low priority idle loop increments the
counter.frContextTime - Test to determine context switch time with a semaphore.
frFastLogger - Data logger optimized for 328 Arduino. Logs two analog pins
every two ticks (1024 usec tick).frJitter - Test of jitter in sleep for one tick.
frMegaLogger - Data logger optimized for Mega. Logs four analog pins
every tick (976 samples per sec, four values per sample)