The latest official MicroBlaze port and associated documentation is located here:
http://www.freertos.org/Free-RTOS-for-Xilinx-MicroBlaze-on-Spartan-6-FPGA.html
This MicroBlaze port is produced using version 13.1 of the Xilinx ISE Design Suite (Embedded Edition), supports version 8.10 of the MicroBlaze soft processor core, and was developed and tested on a Spartan-6 FPGA based SP605 Evaluation Kit.