question about 3v3 line being pulled low by a 5v microprocessor

Question, and yes, I know it's a dumb one, but google hasn't confirmed my thoughts.

I know that if you want to interface 5V logic with another voltage, like 3v3, you have to use a voltage divider or other level translating parts to safely not fry the lower voltage logic, however, does the same hold true for just pulling something low?

If you have a 3v3 IC, say a bluetooth module, and you hook it's reset pin to a 5V ATMega328p, if you set the ATMegas pin as "OUTPUT" and set it to Low (to reset the bluetooth module) do you still need level translation pieces in there, or not, since it's just going low? I'm pretty sure the answer is no, since it's sending a 0, and pulling it to 5V, but just want to be sure before I fry something.

I know that if you want to interface 5V logic with another voltage, like 3v3, you have to use a voltage divider or other level translating parts to safely not fry the lower voltage logic, however, does the same hold true for just pulling something low?

No.

If you have a 3v3 IC, say a bluetooth module, and you hook it's reset pin to a 5V ATMega328p, if you set the ATMegas pin as "OUTPUT" and set it to Low (to reset the bluetooth module) do you still need level translation pieces in there

No.

pinMode( BLUETOOTH_RESET_PIN, INPUT );

...allows the pin to "float". A pull-up resistor on the line allows it to float to 3.3v.

pinMode( BLUETOOTH_RESET_PIN, OUTPUT );

...switches the pin to a "sinking" output which pulls the line to ground.

Obviously, a HIGH OUTPUT is a big no-no.

INPUT w/ INTERNAL PULLUP is debatable...
http://arduino.cc/pipermail/developers_arduino.cc/2011-September/005568.html
http://arduino.cc/pipermail/developers_arduino.cc/2011-September/005607.html

So, the pin can safely be INPUT (no internal pullup) or LOW OUTPUT. With one caveat: do not exceed the maximum current flow.

yeah I'm not putting it high, there's a 10k resistor pulling the BT modules reset pin high, but i want to be able to reset it from the microcontroller, so I'd set
say:

pinMode(BLUETOOTH_RESET_PIN, OUTPUT );
delay(100);                  // waits for a little
  digitalWrite(BLUETOOTH_RESET_PIN, LOW);    // reset bt module
  delay(10);       
pinMode( BLUETOOTH_RESET_PIN, INPUT );

Like that.. correct?

The digitalWrite is not necessary.

The digitalWrite is a safety feature, say some library has set that pin high by mistake ?

The robust way to pull a 3V3 line low from 5V device is via a diode - then you can't damage it whatever the software does because you can only pull down.