If you're looking for a fun day trip, I suggest visiting the Portland Headlight and Fort Williams Park in Cape Elizabeth. I decided to go on a wim yesterday and it was great! The views are beautiful, I could just stand there (or sit on one of the many benches) and look out at the water for ages. There's a small museum (only $2 admission), I didn't think it was that spectacular but there was a short video playing that I found interesting. There's a gift shop as well with some very nice items, although too expensive for a college student lol. What I liked most about the park was the pathway that led along the water and all the way down to the actual park where there's even a small beach. It was quite the hike! It was very hilly, but there were benches placed strategically throughout that gave excellent views of the lighthouse and water. The beach was awesome, very small, but instead of sand (just a small strip right before the water) there were large, round rocks. Past the beach are some more historical landmarks (Fort Williams) to check out.
If you do decide to go, I advise you NOT to follow the directions on the official website. They look really easy and simple, but after driving around Portland for nearly an hour I realized they weren't. After driving past the Casco Bay bridge for the 3rd time I decided to cross it just for the heck of it, and sure enough there was the sign directing the way to Cape Elizabeth! So frusturating.