ATtiny85 communication with computer through USB
Digispark made a lot of these as part of a "cheap Arduino USB interface" project a while back.

This is my Digispark, it's pretty cute:



They have a web page here.



I got them for about $2 each. The board has the ATtiny85, a voltage regulator, and a handful of other parts.

Schematic (courtesy of Digistump Wiki):





More information about the Virtual USB idea at USB-Keyboard with Arduino and V-USB library, an example.