On the ATmega168 (and the ATmega8), the analog input pins can be used as normal digital i/o pins (except for analog inputs 6 and 7 on the surface mount versions of the ATmega168 on, for example, the Arduino Mini). We'll probably retain "hidden" support in the software for using these as digital pins 14-19, but if not, you could still read from the PORTC register directly.