Adafruit has made an I2C interface for four rotary encoders. It comes in the form of a PCB with four footprints that accept one of the most common rotary encoder forms (Bournes PEC11 horizontal style) ...
A while back, [Rupert] wrote a blog post on using V-USB with the very small, 8-pin ATtiny85. Since then, the space of dev boards for 8-pin micros with USB has exploded, the most recent being ...