What is Letterboxing? Michelle Spalding offers a history of letterboxing in England and the United States with bibliography.
Dutch Letterbox Site Clues for boxes in Dartmoor and in the Netherlands. [English and Dutch]
Letterboxers Anonymous Forum with clues and discussion topics. Includes helpful hints on methods and supplies.
Aisling Dart Artist from Salem, Massachusetts describes her boxes.
Letterboxing Northeast The Drew family of East Lyme, Connecticut, offer clues in New England states as well as Washington, DC, South Carolina, and Colorado.
Mark and Sue Pepe Couple from Kensington, Connecticut describe activities in eleven states and the island of Aruba.
MommaFox and Bald Eagle Anna and Paul offer clues to boxes in Connecticut, Massachusetts and Vermont.
The Space Traveler Family offers clues for Pennsylvania, New York and other states.
Letterboxing Questionnaire British university student studying letterboxing for her dissertation asks visitors to answer a few questions on the activity.
Urban Letterboxing Database of clues to letterboxes in urban locations, primarily in Europe.
Stamp-in-the-Box A collection of information and clues relating to letterboxing, a hobby that combines hiking, art, orienteering and mystery in a treasure-hunt style activity.
Nebraska Letterboxing Information about letterboxing in and around Nebraska. Includes clues and logs for local letterboxes, as well as some resources for letterboxing in general.