In August, I would avoid Cape Cod and Martha's Vinyard. Beautiful places, but they are so crowded they are difficult to navigate.
I have often done the drive from Boston, up to Portland, Maine. Boston is a great city to photograph. Full of history, small neighborhoods, great buildings.You pass through the little sea-side town of Portsmounth, New Hampshire, which has a great "old New England" feel, with a beautiful church in the square and some cobblestone streets. Be sure to drop by the Portsmouth Brewery for dinner. Then continue north. When you get to Cape Elizabeth, Maine, check out the
Portland Head lighthouse, which is one of the most picturesque lighthouses (made famous by a painting by Edward Hopper). Then stay in Portland awhile. Great restaurants, and active boat yard and harbour, brick streets, and some beautiful Victorian buildings. (Like San Francisco, Portland suffered a major fire around 1900, and so many of its buildings were rebuilt with Victorians). Then, keep driving north along the ocean.
Another beautiful area is
Northampton, Massachusetts, in the middle of the state. A great college town (with 4 colleges and one university nearby) with a lot of old character (and again, great food). Drive up Mount Holyoke for a view of the whole Connecticut River Valley. The little preserved town of Deerfield gives a glimpse of how the towns used to look way back. Drive north to the tiny town of Montague and visit the
Book Mill, a used book store/restaurant in an old mill on a great little stream. Drive north to Brattleboro, Vermont, and then you can meander up north, or head west over the rolling hills.
Hope this helps.
Dan