Ran across this neat article and video at Make Magazine. They attached an Arduino to a candy vending machine, and connected it to the internet so you can pay for the candy using paypal. A fascinating and intriguing project:
http://blog.makezine.com/archive/2010/10/paypal_vending_machine.html - While walking the show floor at the PayPal X Innovate 2010 developers conference today I came across this cool PayPal vending machine prototype. Ray Tanaka and his crew at PayPal Labs hacked together the multi-part system using a mechanical candy dispenser, a couple of Arduino Duemilanove, aWiShield, relay, proximity sensor, and LED display. The end result allows you to scan a QR code, make a payment, and acquire munchies using a smartphone. As you make your payment, the machine will tweet your purchase and notify a confirmation display.