XmegaDuino alpha 1, based on arduino 0018 is now ready, targetting only the atmel xplain evaluation board. http://code.google.com/p/xmegaduino/. Rene Bohne' is the other half of the XmegaDuino team. Eberhard Fahle is the third half, having given us a lot of help trying things out. He's also developing his own xmega project. Check it out at http://code.google.com/p/xmlibraries/.
The Arduino basics work: serial I/O, digital I/O, analog input, PWM, millis/micros, delay/delayMicroseconds, and interrupts.
None of the libraries have been ported. I'll be looking at some of them soon. If anyone wants to try to port any of them before I get to them, I'd be very pleased. Just let me know so we don't duplicate each others efforts.
But before that, next up for me is porting to the sparkfun xmega100 breakout board. Then on to the libraries.
If you give XmegaDuino a shot, let us know how it goes. I won't have a lot of time for support, but I'll do what I can. Please file bugs/issues so we can keep track of what doesn't work, and what new stuff folks want.