EswarD2 @ instructables.com has build an Arduino based door lock using Arduino UNO, a keypad and a servo motor.
This a door lock built as fun project.It is quite easy to build and a fun way to learn and improve your knowledge of arduino.I tried to add a 16*2 display but there werent enough GPIO pins on arduino Uno.If You are interested in adding a display you would need an arduino Mega.
ArdLock – Arduino Door Lock – [Link]
Marked