Just received an e-mail from Circuit Cellar (http://www.circuitcellar.com) that they have a design contest planned for later this year based on the Atmel Zigbee chips.
It's not yet officially announced except to say it's on the way.
For those that don't know, Steve Ciarcia's Circuit Cellar has been around for quite a long time - I knew it from Byte Magazine but now it's a stand-alone magazine (both electronic and print) that has some very excellent articles in it and quite a few feature the AVR.
Their last finished contest was an AVR contest and as I recall, Colin O'Flynn was a finalist.
Anyway, just a heads-up... Zigbee stuff is coming.