Holy sh!t Nate, that's a major task. The White Mountain National Forest is almost 800,000 acres and there's a ton of riding in there, not to mention public and private lands (where a lot of the goods are found) outside the WMNF .
I have hit the Franconia area a couple times this spring and I am blown away by the quantity and quality of singletrack there. Some may wonder why I feel KT is over-hyped (nice signs and map, though); one ride in this area and you should understand. Littleton and Plymouth both offer tons of amazing riding,
Littleton Bike & Fitness and
Rhino Bikes are the places for ride info. I owe it to myself to explore these areas more. And I will, dammit!
Here in North Conway,
Red Jersey Cyclery is probably the best shop for beta. There are a couple of very good maps (Rob Brook area of the Kanc, and Conway area map) that will get you around. Sometimes the best stuff is not on the map but people often find it anyway. I could not, and would not, attempt to post such info on the web. For one, there are few signs and descriptions would be very difficult at best. Two, some of these trails are on private property and while the owners tolerate us they would not tolerate us promoting public use of their lands.
A ride I can recommend in this neck of the woods is climbing the Red Tail Trail (shuttle if you're a flatlander and can't deal with a dose of climbing humility), then descend the Black Cap Connector (Gnar with a capital G). Decending RT is also a good option, both are very long descents. Connect with the Sidehill trail from the intersection with Middle Mountain Trail, follow it to the powerlines (multiple options), then back through Sticks & Stones and the Pudding Pond Loop. All this is on the Conway area map.
I would offer a tour but that's on hold for the moment.
