I'm too high maintence to camp - - but pretty much all of southern maine is relatively quiet - you just want to stay away from Bangor, Portland, and the other cities...
http://www.campmaine.com/ has a pretty extensive list of campgrounds based on region...
I'm real partial to the south coast region Ogunquit is beautiful, but a little touristy - kind of like the cape but wiht much fewer people. Kittery would appeal to the shopper in your, if it exists, it's got tons and tons of outlet shopping.
The midcoast region is also a little more rustic, but wiht tons of history - and much of maines maritime history comes from that area (I like boats and boating, so this is my favorite area). Whale watching is also available
Further north is the Moosehead area and moosehead lake-- stunning scenery... it doesn't get any better than t hat.