ManiacBug has ported the powerful Contiki operating system to the Zigduino. Contiki provides a complete 802.15.4 stack and 6LowPAN (IPv6) in a fully open source package. That means that we now have fully open software stack to go with our open hardware. Contiki is the also the solution Atmel is currently recommending for running 6LowPAN on its wireless hardware.
The goal of Contiki to provide a common operating system for embedded devices -- the 'Internet of Things'. It has some issues with bloat and lack of focus due to its origins as a research platform, but ManiacBug has trimmed the package down to only what is required for running on the Zigduino. One of the very nice things that it has available is desktop tools that interface to the hardware for inspecting network traffic and measuring performance.
In order to properly maintain the platform, ManiacBug has created a fork of Contiki on github, contiki-avr-zigduino.