From http://arduino.cc/forum/index.php?topic=80928.0

From http://arduino.cc/forum/index.php?topic=80928.0

/*
* Theory: all IO pins on Atmega168 are covered by Pin Change Interrupts.
* The PCINT corresponding to the pin must be enabled and masked, and
* an ISR routine provided. Since PCINTs are per port, not per pin, the ISR
* must use some logic to actually implement a per-pin interrupt service.
*/

/* Pin to interrupt map:
* D0-D7 = PCINT 16-23 = PCIR2 = PD = PCIE2 = pcmsk2
* D8-D13 = PCINT 0-5 = PCIR0 = PB = PCIE0 = pcmsk0
* A0-A5 (D14-D19) = PCINT 8-13 = PCIR1 = PC = PCIE1 = pcmsk1
*/

Setup:

PCMSK2 |= (1<<PCINT23);
PCICR |= (1 << PCIE2);
PCMSK0 |= (1<<PCINT0);
PCICR |= (1 << PCIE0);
ISR(PCINT2_vect)




ISR(PCINT0_vect)
{
code here
}