Here is a great little project by Kevin Kadooka if you are starting out on photography and have good Arduino understanding, or if you are starting out on Arduino and have a solid understanding of photography :)
This solenoid based single leaf shutter is controlled by Arduino and can expose a sensor or film for anywhere between 1/125 to infinity at the press of a button. The exposure duration is controlled via a small potentiometer.
P.S. Kevin is the brains behind the wonderful DUO TLR which we featured way back.