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) ...
TI’s MSP430 chips are rather interesting – they’re low power, very capable, and available for under a dollar in most cases. Some of these chips, though, don’t have native SPI or I2C interfaces; ...