http://www.waterwayguide.com/guide/northern

You can get it from Amazon, West Marine, etc.

As for non electronic navigation, i.e., traditional, skilled (alive, but not) dead reckoning -- there were people plying such waters long before we had all these "convenineces". While just like you shouldn't let people learn arithmetic, geometry, algerbra, etc. with calculators; after you have learned how to navigate "traditionally", electronic assistance is more than just a conveninece. In some cases, you really won't be able to deduce the "local" conditions from published charts. You'd have to begin adjusting your timing, course, etc. to deal with your limitations of information. I believe that if you have it, and it makes sense, USE IT. Knowing how to do it manually is necessary because if you lose the equipment, power, etc. -- then you've got a back-up.

In some situations, no having a chart plotted and tracked makes the passage a very different experience. A passage through the Muscle Ridge Channel, for example, can become a nail bighting experience (or worse) if you don't really know what's happening with cross currents and WHERE YOU REALLY ARE -- and where you really are going. If you add a bit of fog and wind (which are hardly mutually exclusive in Maine); and, you add some other traffic, lobster pots, etc. A chart plotter with a safe route to follow makes a big difference to me.

For most little passages, in the right weather and wind, you don't NEED a chart plotter. But things can change during the day. Also, you're crew members may not be as diligent at monitoring where they are and are going. If you lose track of where you are, one beautiful forested island looks very similar to another -- and so on.