A functional clock which displays the time in words in increments of 5 minutes. It uses multiplexing to control a gridded array of LEDs and uses 74HC595 Shift Registers. It is written for the Attiny2313 but could be easily be adapted for any microcontroller. The RTC Clock is the DS1307.
A detailed explaination of the design process of hardware selection is available at: http://no8hacks.com/blog/2012/8/16/led-word-clock
Interactive schematics and BOM are also available at: http://upverter.com/bverc/5d5df4dc0c286f73/LED-Word-Clock/
The TWI drivers are implemented using drivers written by doctek. His detailed instrucable is available: http://www.instructables.com/id/I2C_Bus_for_ATtiny_and_ATmega/