Dive Winnipesaukee does charters
www.divewinnipesaukee.com/ Other than that I don't know of anybody who does, Central NH Divers may
http://www.productiontraileranddock....lnhdivers.html they're great guys as well and if you're in the area I'd recommend talking to both of them.
Right now I don't think anybody is offering tours, but in few weeks once there's ice over the lake most of the NH dive shops offer Ice Diving trips and classes if you're interested in diving under the ice. Once summer rolls around lots of us who frequent this board dive, and always want new dive partners (although we don't offer tours, just friendly dive buddies)
Hubbles