Definitely Saco Heath and Cascade Falls; and Fuller Farm is another nice one. If you're looking for hikes with elevation, you need to travel a bit further (either south to Agamenticus or northwest to the Fryeburg area).

OP, I'm a bit late to the game but just wanted to give my two cents. As others have said, Maine Memory Network is the place to go for photos. The Maine Newspaper Project is another favorite of mine, it has digital records of local newspapers (broken up by county). The stories and ads are useful for getting an idea of what life was like and what people were talking about at the time. Good luck!