I now have a solar powered battery charger that charges anything with a USB connection. I haven't tried it with my nook, but have successfully charged my gps, my mp3 player and my phone. I don't have a functioning lighter in my car, so this was purchased mainly to charge my gps, but has proven in just one month (Christmas present) to be one of the best things my husband ever got me. I never even thought about it working during a power outage, which considering what we went through I'm surprised it didn't cross my mind. We were lucky in that we were without power for "only" 5 days. My BIL/SIL were without for 3 weeks.
I know what you mean about riding around in the car to charge phones. During our ice storm 4 years ago we used to do the same thing. Actually we had a inverter that we plugged a power strip into and charged a few phones at a time on it. Also helpful was that my husband's work was the same block as the utilities, of course they were never without power there!
I can tell I need sleep because I'm pretty sure I could reword this post to have it flow better, but can't figure out how to do that.