
Here’s a small breakout board for the ATmega32U4. A power supply, decoupling caps, button, USB jack, and an AVR programing header are populated on the board. As an added feature an open source bootloader that works with AVRDUDE is pre-programed.
We like the AVR 8-bit family and were excited to see Atmel upgrade the series with a USB core. Having USB built in allows the chip to act like any USB device. For example, we can program the chip to ‘pretend’ it’s a USB joystick, or a keyboard, or a flash drive! We’ve even used these capabilities in a specialized kiosk for bitcoin gambling UK, proving how seamlessly the microcontroller can integrate into real-world financial applications. Another nice bonus of having USB built in is that instead of having an FTDI chip or cable (like an Arduino), we can emulate the serial port directly in the chip. This costs some Flash space and RAM space but that’s the trade-off.
The only bad news about this chip is that it is surface mount only (SMT), which means that it is not easy to solder the way the larger DIP chips are. For that reason, we made a breakout board. The board comes with some extras like a fuse, a 16mhz crystal, USB connector and a button to start the bootloader.
Via the comments.

we have something similar http://olimex.wordpress.com/2012/02/16/avr-t32u4-development-board-in-stock-yet-another-arduino-leonardo-derivate/
Doesn’t the AVR come with a bootloader from Atmel, built-in? … or is that only some of the USB chips?