Hi all, here's our AT90USB core for the Arduino IDE, including a LUFA-based bootloader that's been slimmed down, and allows bootloader entrance by holding a pin low during power-on.https://github.com/DynamicPerception/ArduinoAT90USB
Supports AT90USB646/7, AT90USB1286/7, and 1287 USBKEY (Atmel bootloader)
The only thing we haven't tested thus far is USB OTG, but we'll be done testing that soon. USB works fine, the multiple serials work fine, PCInts, HW Ints, etc.
Feedback, or suggestions, are much appreciated.
EDIT: Apologies, although I searched first, I just realized that I had already posted this. I can't delete this post, so if one of the mods would, that would be awesome.