Brendan built a breakout board for the 44pin QFN ATxmega uC. He designed the board to have a USB connection and a 500mA 3.3V power supply. 30 of the pins were broken out to two rows of 0.1” pinheaders on either side of the board. You can download the source files from GitHub.
I recently assembled the first revision of my XMega breakout board. The idea was to create a very simple breakout board that fit well on a breadboard, used the Arduino IDE and libraries, and had a USB bootloader. In order to make the board as thin as possible, I used the QFN version of the XMega. I re-flowed the board in a toaster oven and the QFN soldered without any trouble.
Via the forum.