I've stayed at Paugus Bay Campground (
http://www.geocities.com/weirs_pbc) several times, although not in the past several years, and have always had great service. They are right on the water, and have docking, although they are accessible only by going under a railroad bridge that allows passage for only small boats (under 20 ft?). They are also within walking distance of the Weirs.
I've also stayed at Clearwater Campground (
http://www.clearwatercampground.com/), and although not right on the big lake, it also is a very nice campground and not too far from the Lake.
Good Luck!
Wolfeboro Matt