We stopped in Portland to try Bite into Maine, a food truck that has been earning all the accolades. They offer both traditional (mayo or butter) and non-traditional styles (Wasabi, Curry, & Chipotle) of lobster rolls, as well as a vegetarian sandwich of the day.

I went for the traditional Maine style (mayo and chives, $15). Steve had a TMB sandwich (local tomato, mozzarella, and basil on grilled Italian bread, $7). My lobster was great; there was a generous amount of tender, sweet lobster, kissed with mayo, brightened by the chives. The roll was buttered and grilled. Steve loved his sandwich as well.
The truck is parked at Cape Elizabeth. We enjoyed our sandwiches at a nearby picnic table and relished the gentle breeze with the beautiful view of the water. It was a perfect Maine lunch.

http://www.biteintomaine.com/