The AT90USB162 is the easiest way to add USB functionality to your next device, Atmel provide free open source HID (mouse, keyboard) and CDC (USB-to-RS232) code and on top of this AT90USB162 cost is same as ATMega16, so what you are waitng for? AVR-USB-162 board provide the basic circuit necessary to work with AT90USB162 - USB connector and circuit, external power supply if your circuit require more power than 100mA which usually USB port provide, button, status LED, reset button. All AT90USB162 come from Atmel pre-programmed with bootloader which allow code to be programmed inside the chip without any external programmer, just download the FLIP software from Atmel web site and load your HEX code inside AT90USB162.