The North Shore [1] abounds in gorgeous beachfront. One of the very best in New England is Crane Beach (Argilla Rd., Ipswich, 978/356-4354, www.thetrustees.org [2]), a four-mile stretch of white sands and crashing white surf. The only time it isn’t idyllic is the brief period of greenhead fly season (usually late July or early August—call ahead to check).
The half-mile Good Harbor Beach (Thatcher Rd./Rte. 127A, Gloucester) offers a range of terrain, including sandy barrier beach, salt marsh, and rocky headland for tidepooling.
The more secluded Singing Beach (Masconomo St., Manchester) is named for an interesting phenomenon wherein under certain conditions the sand seems to sing—or more accurately, squeak—when you walk on it.
Links:
[1] http://www.moon.com/destinations/new-england/massachusetts/eastern-massachusetts/the-north-shore
[2] http://www.thetrustees.org