I know the limits for each pin, is there a combined limit for all pins together I need to be aware of? I'm coming from the basic stamp, and I had to watch it to make sure I wasn't using too many pins at once at full current.
200mA
It's 200mA total but there are some sub totals as well:-
Although each I/O port can source more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient).
ATmega88/168:
1] The sum of all IOH, for ports C0 - C5, should not exceed 100 mA.
2] The sum of all IOH, for ports C6, D0 - D4, should not exceed 100 mA.
3] The sum of all IOH, for ports B0 - B7, D5 - D7, should not exceed 100 mA.
There is a similar limit for sinking.