Check out the latest Analogue to Digital Conversion Interrupts on an ATmega168A tutorial over at Protostack. You might not need the information today but it will probably come in handy some day!
“In this tutorial we add a second analogue input and use the ADC Conversion Complete interrupt. The circuit we are using is similar to what we used last time but has an extra trimpot and uses an ATmega168A microcontroller.”