Arduino and the Atmega Microcontrollers?

Thank you. I'm glad to learn that I can use the Arduino programming and bootloader on other 8bit processors from Atmel. That was what I wanted to know so I wasn't stuck being able to only use a few mcu's. Would be nice if it grows to supports some of the larger mcu's from Atmel in the future.

Since a board like the Uno uses 2 Atmel mcu's (one for the USB and one for the program), if I was building my own PCB - do I need to program that USB mcu with any special bootloader or program?

Kindest Regards,

DataCrypt