Best beach camping on the east coast?

If you are willing to backpack your gear to a site miles down the beach there are walk in campsites along Assateague Island. You can't just camp anywhere, though, and you need a permit (last time I was there it was free). They are primitive sites though, no water or facilities and the hike takes several hours. But the location is beautiful, you are right over a small dune from the sea and there is no one else around except other tent campers. The truth is, it is rare to find any area where you will be allowed to camp directly on any beach, public or private. Camping, even with tents, is damaging to fragile beach ecology and interferes with the natural processes of animals that use the areas after dark. So the best you can hope for is near the beach to set up your tent, usually behind a dune or protective line of trees.

Hither Hill State Park on Long Island is a great place to camp. It's right on the ocean, very clean and family friendly. It's not too far of a drive for entertainment or a meal.