Simple USB Device
This is the circuit from the AVR ATtiny USB Tutorial from http://codeandlife.com
The tutorial of codeandlife.com is a nice tutorial on how to use the V-USB with an AtTiny2313 to build your own USB device.
An important point to mention is, that the V-USB library works only with few clock frequencies (12 MHz, 12.8 MHz, 15 MHz, 16 MHz, 16.5 MHz, 18 MHz and 20 MHz)