FreeRTOS demos are provided that target microcontrollers from the following manufacturers:
Demos targeting Altera products
Microchip also have an application note showing how to integrate their libraries and stacks with FreeRTOS - with full source code being provided too.
Please note that the segmented memory on the PIC18 makes it a less than ideal candidate for use with an RTOS.
Note! there is now a supported IAR/MSP430 port in the FreeRTOS download that is yet to be documented. The demo is basically the same as the other MSP430 demos, and the IAR project can be located in the FreeRTOS/Demo/msp430_IAR directory.