I just sent the latest zigduino revision out for fabrication. This is the final production prototype; the panel also included a test jig and a couple of interesting development boards. The changes to this revision are mostly cosmetic cleanup and additional test points. There are two significant functional changes for this revision.
First, I added an SPI header parallel to the matching pins on the digital header. A solder jumper on the back of the board allows digital pin 11 allows it to be either a PWM pin or the MOSI pin, for full shield compatibility.
Second, I added RF TX and RX LEDs near the ISP header. These are independent pins (23 and 24), and can be used as indicator lights for other purposes if they are not needed for the particular radio application.
I've also opened a GitHub repository for the ported bootloader and Arduino core. The bootloader works, but I haven't fully tested it yet. The core libraries work well enough for hardware test, but have likewise not been fully wrung out. This package includes board definition files for Atmel's IEEE 802.15.4 MAC library. Additionally, you may wish to check out Atmel's 6LoWPAN (IPv6 under 802.15.4) and BitCloud (ZigBee Pro) libraries as well.
I'm looking forward to getting the boards out early next year. Watch this space for more updates.