Letterboxers Anonymous - Forum with clues and discussion topics. Includes helpful hints on methods and supplies.
Letterboxing Germany - Clues for Germany and other European countries. Includes photos and tips. [English, German]
Letterboxing Minnesota - Includes letterboxing basics and clues for Minnesota letterboxes.
Letterboxing Northeast - The Drew family of East Lyme, Connecticut, offer clues in New England states as well as Washington, DC, South Carolina, and Colorado.
Letterboxing Questionnaire - British university student studying letterboxing for her dissertation asks visitors to answer a few questions on the activity.
Mark and Sue Pepe - Couple from Kensington, Connecticut describe activities in eleven states and the island of Aruba.
Ryan's Letterboxes - Personal page with clues for boxes placed throughout the western United States, as well as a few in Canada, Africa, and Central America. Also includes tips for improving the stamp quality.
Silent Doug's Letterboxing Site - Articles including getting started, outdoor ethics, and explanation of cryptic letterboxer codes. Also includes list of boxes found and clues for boxes placed in the northeastern region of the United States.
Silver Eagle's Letterbox Aerie - Clues to nearly 100 letterboxes that Silver Eagle has placed in North America, primarily in Texas.
The Space Traveler - Family offers clues for Pennsylvania, New York and other states.
Twograysquirrels Letterboxes - Clues to letterboxes placed by twograysquirrels, mostly in Maryland and Virginia.
Urban Letterboxing - Database of clues to letterboxes in urban locations, primarily in Europe.
Wanda and Pete's Letterboxes - Clues for boxes placed primarily in Rhode Island, but a few in other states as well. Also includes logs of the movement of hitchhiker boxes, primarily in New England.
What is Letterboxing? - Michelle Spalding offers a history of letterboxing in England and the United States with bibliography.
NPR : Letterboxing - Radio host Linda Wertheimer and Thomas Johnston, an enthusiast in Washington, D.C., find a letterbox near the White House. [audio] (April 10, 2004)