Davide Gironi has posted an I2C multiple HD44780 AVR Atmega library:
This library implements a driver for HD44780 lcd connected through PCF8574 port expander.
Data is transmitted using only 2 wire over i2c with the PCF8574.
This library can drive up to 8 LCD concurrently.
Lcd driver is based upon Peter Fleury’s lcd driver
HD44780 to i2c library its based upon this library
More details at Davide Gironi’s blog.
Check out the video after the break.