Well, I just returned from a visit to Maine, and I stopped at two different shops. Pen Ventures in West Rockport was a very nice, small shop. The owner was a delight- couldn't wait to show me the new product, helping me with design ideas. I'm new to scenic stamping and she was very helpful- I hope to return there again because I was so pleased. She had Copics and a good selection of inks, but mostly scenic stamps. It's a VERY small store, but if you are into scenic stamping then it's well worth the trip.
The other store I topped at was Silver Fox Stamps in Winslow. The tiny little shop is in the owners home, and her husband was very kind to let me in long after he had closed for the day. They make their own wood-mount red rubber stamps, so this is worth the trip just to find some unique design you'll never find elsewhere. But they have an online catalog so check them out before you go because otherwise there's not much else. Still, I was very pleased with my purchase and would stop there again.
I've been to Maine-ly Stamps a couple times and not too impressed. But they do have a lot of stamps. Prices are high.