Here are some links to sites that you might also be interested in visiting.

Town of Londonderry
State of New Hampshire
Windham Rail Alliance 
NH Outdoors 
newhampshire.com
Granite State Wheelmen
Appalachian Mountain Club 
hikeSafe There and Back
NH Bicycle/Pedestrian Information
Rails to Trails Conservancy
League of American Bicyclists
Rail-Trails in New England
New Hampshire Cycling Club
T-Bone (Tandem Bicyclists of New England) 
Seacoast Area Bicycle Routes
Guide to NH Trails
Peak to Peak
FOMBA (Friends of Massabesic Bicycling Association)

Here are some magazines

Bicycling Magazine
Mountain Bike Magazine
Backpacker.com