Gershel, keep in mind that in many of the more remote spots in Maine, you can
anchor for free. Merchant''s Row, Seal Bay and Winter Harbor on Vinalhaven, Duck Harbor on Isle Au Haut come to mind. Of course these places don''t have the amenities that some people crave, but they''re awfully nice.
Otherwise, $20/night for a mooring is about average. You''ll pay more in places like Buck Harbor and Southwest (especially if you rent from Hinckley); less in some other spots. I''m not sure about dock space because we so rarely use it, but I think the going rate is $1.75/foot in my home port in Casco Bay, higher in places like Camden, lower in others.
Get the Taft guide - Cruising Guide to the Maine Coast. That and a few
charts and you''ll have all the information you need.