Was just thinking about about when the Arduino is in sleep mode - what happens to the output pins?
Do they remain in the state they were (possibly still sinking/sourcing current, or do they go into a tristate?
Cheers
Hi Marvin,
You might want to check the product manual (look for power management and sleep modes section) as there are six different sleep modes for ATmega328p. Among the six modes, I believe the pins will continue to work (i.e. hold the value) in Idle and ADC Noise Reduction modes.
Do they remain in the state they were (possibly still sinking/sourcing current,
Yes.
or do they go into a tristate?
No.
The more complex the I/O function, the more likely it will be turned off. For example: for most sleep modes PWM stops. Simple I/O always remains functional.
Cheers for the clarifications! 
You are welcome.
If your application will be battery powered, this may help...
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1243213127/all
Basically, floating digital inputs will consume power even if the processor is sleeping.