I don't have any example code, but it looks like you need to make sure to:
# setup up the mux register for the analog inputs.
# setup the gain register for these inputs. Not all of the analog inputs have a gain setting.
# Control the ADC with the ADC Control and Status Register – ADCSR
Here is a link to the "datasheet":http://www.atmel.com/dyn/resources/prod_documents/doc2503.pdf but you probably all ready have that.