I was looking for one place that had all the info, but couldn't find one, so here are the options to watch from water--for landlubbers, check here:
http://www.nhmagazine.com/NH-Fourth-of-July-Events/.
July 3rd:
Weirs Beach: 11:59 (Boardwalk)
July 4th:
Moultonborough/Center Harbor: Dusk (Center Harbor Beach/Harbor)
Meredith: Dusk (Bay)
Wolfeboro: 9:30 (Bay--I saw these last year, and it was super cool because there are a few different groups of people who do their own--about a full hour show, all together)