I made a photo booth which was installed inside of an old phone booth in a local cafe for a new-media art festival this past summer. I used a Raspberry Pi, a usb webcam, a big red button connected via GPIO, a coin slot connected via GPIO, and an ethernet cable running to the router in the back room. People would insert their dime or two nickles and the button would light up. Pressing the button would take a photo. The Pi then uploaded the photos to a website which looped through all of the photos taken during the festival. People could visit the website on their own devices, but there were also a few screens set up around the town in shop windows displaying the photos. The program to do all this was a simple python script with a loop.
You can still see the photos taken here: http://donttakemypicture.org/