I have an '01 Durango that has a power drain. I hooked up a meter on the negative side and it showed 12.3. I started pulling fuses from both fuse panels and didn't see a drop. I disconnected the positive cable from the fuse panel and the power drain dropped off to 0.2. What can cause this and what should I do to fix it?
This is not a power drain, this is normal. Your battery will sit at ~12.4 V with the car off. You can pull out all the fuses in the world, you can even take the battery out of the vehicle and carry it a full mile away from your vehicle, it will still read ~12.4 V.
If you are really investigating a power drain, you need to measure current, not voltage. Repeat your procedure (you were doing the right thing), just switch your meter to DC amps.