Okay, it's easy enough to drive a 7-segment common cathode display with an Arduino. Simply connect the output pins of the Arduino to resistors and then tie each resistor directly to a corresponding segment on the display. The common cathode goes to ground on the Arduino board. How do I go about driving a common anode display with same? I think (and correct me if I'm wrong) I could use an NPN transistor in series with each segment and let the output of the Duemilanove's pins drive the bases of the transistors. Am I thinking along the right lines here? I know with this idea I would need seven transistors for each display but I thought it would be a good project for a snowy night (I live in Maine, USA where such events are imminent) I want to be sure this isn't a half-baked idea which would fully bake my Arduino 
I appreciate any advice people give me. 
I think (and correct me if I'm wrong) I could use an NPN transistor in series with each segment
Well I would use a PNP transistor or P-type MOSFET
Or just connect the common anode to Vcc, individual resistors from the cathodes to Arduino pins, and invert the sense of your outputs, i.e., write a zero to turn a segment on and a one to turn it off. IIRC, the pins can sink as much current as they can drive.
Or just connect the common anode to Vcc, individual resistors from the cathodes to Arduino pins, and invert the sense of your outputs, i.e., write a zero to turn a segment on and a one to turn it off. IIRC, the pins can sink as much current as they can drive.
Yep, that's the way to do it. Let the software do the heavy lifting.
Lefty
I never thought of these. I'll have to try them out! Thanks again folks!