Hello Jake!
I know of several traditional coed summer camps both in the New Hampshire and areas. I'll recommend several for now and then I'll refer you to a website that I used, that will provide you with more options.
The first camp I would recommend looking into is Camp Hawkeye in Moultonborough, NH. It is a wonderful summer camp that focuses on more wilderness and adventurous activities.
http://www.choicecamps.com/overnight-summer-camps/new-hampshire/camp-hawkeye/112/
Camp Walt Whitman is a coed summer camp taht consists of a variety of excellent adventures for campers. This sleep away camp offers a variety of indoor and outdoor activities, including photography classes, ropes courses, and windsurfing.
http://www.choicecamps.com/overnight-summer-camps/new-hampshire/camp-walt-whitman/104/
There is also an arts summer camp that I know of up in Maine that is really great. It's called Camp Med-O-Lark. And although it's technically a general arts camp, it has many aspects of a traditional overnight camp. Camp Med-O-Lark offers a variety of remarkable indoor and outdoor activities such as kayaking, rock climbing, animal care, and dance!
http://www.choicecamps.com/search/overnight-camps/results?s=med-o-lark
Maine Teen Camp is another neat overnight camp that specialized in music and gives campers the chance to compose songs, create band groups, and more! The summer camp also has a recording studio which is awesome!
http://www.choicecamps.com/overnight-summer-camps/maine/maine-teen-camp/48/
Also, it may be helpful for you to check out this website: http://www.choicecamps.com. You can take a look at more summer camp options in your area and throughout the country. Also, you can compare camps, watch dvds, view pictures, and check out their activities.
I hope this information is helpful to you!
~Jessy~