For this week I connected two MCUs via Xbee. Which is suuper easy. Zigbee uses standard serial, basically if you have a serial talking MCU to the Xbee's Tx/Rx line you are done. Almost...you have to first set up the Xbees so they will listen to each other, and they will use the same channel and baud rate. That's it, tutorial here.
ALWAYS use Series 1 Xbees! Series 2 requires too many setup steps, which you will most probably never use!

I am using this circuit to communicate between my board sitting next to the reel and my other board sitting next to my spray cans on the pendulum. It works extremely well, not missing to much information.