- Letterboxing North America WebRing
- Links to dozens of forums and clue sites. - Letterboxing North America - US-based portal offering FAQ, links, forums, and a members-only section where clues can be submitted.
- Letterboxing Germany - Clues for Germany and other European countries. Includes photos and tips. [English, German]
- Massachusetts Letterboxes - Bonnie and Betsey Sennott offer clues to their boxes in Massachusetts.
- 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.
- We Live and Breathe Letterboxing - Accounts, photographs, and memorabilia of the 2008 event as well as an online recreation of the letterboxing museum.
- Chuck's Letterboxing - Chuck and Molly's letterboxes in Connecticut.
- Letterboxing Minnesota - Includes letterboxing basics and clues for Minnesota letterboxes.
- Aisling Dart - Artist from Salem, Massachusetts describes her boxes.
- Dartmoor Letterboxes - Introduction, tips and things to avoid, news, survey, and letterbox clues for the Dartmoor area.
- Have Feet Will Travel - Introduction, contact details, and guidelines for letterboxing in the Dartmoor area.
- Yahoo! Groups: Letterboxing USA - Discussion group for US letterboxers.
- British Columbia Letterboxes - Introduction, photographs of personal stamps, and clues for boxes planted in southwest British Columbia.
- I-95 Letterboxes - Clues to quick and easy letterboxes to find while traveling on Route I-95, from Maine to Florida.
- 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.
- First Finds - Posts first finds submitted by new US letterboxers, organized by state.
- Yahoo! Groups: New Letterboxers Group - Discussion forum and articles for those new to letterboxing.
- New England Area Letterboxing Gatherings - Mark and Sue's weblog of letterboxing events in New England.
- Connecticut Department of Environmental Protection: Letterboxing - Official site supports letterboxing in publicly owned state forests. Includes clues and a map of letterbox sites in state forests.
- History of Dartmoor Letterboxing - Account first published as "More Dartmoor Letterboxes" by Anne Swinscow in 1986.
- The Mapsurfer Treasureboxes - Challenging letterbox clues by Randy Hall, the author of The Letterboxing Companion.
- Atlas Quest Letterboxing - Community with forums, searchable clues, trip planner, recording of finds, event listings, trackers, tutorials, photo galleries, and chat room.
- Letterboxing Questionnaire - British university student studying letterboxing for her dissertation asks visitors to answer a few questions on the activity.
- Dartmoor Letterboxing - Includes a forum, image gallery, map of the area, contact details, and the history of the activity.
- NeeDeep's State Stamp Letterboxes - Ambitious family project placing letterboxes in each state, patterned after the US quarters series.
- Yahoo! Groups: Letterboxing Northeast - Discussion group for the northeastern US.
- Buckaroo's Letterboxing - Clues for boxes she planted in Washington and Massachusetts.
- Urban Letterboxing - Database of clues to letterboxes in urban locations, primarily in Europe.
- New Zealand Letterboxing - Clues, views, and news including boxes from Team Psychokiwi, Judi, Linton, and the Bunny.
- Oklahoma City Letterboxes by Dennis Williams - Clues to boxes in Oklahoma City as well as New Mexico, Alabama, and Costa Rica.
- Kansas Letterboxes - Clues for letterboxes located in Kansas.
- About.com: Letterboxing and Geocaching Attract Walkers - Article describing the basics and the factors that motivate people to start letterboxing.
- Chowder's Southern California Letterboxes - Search for boxes in Long Beach, San Bernardino and Lake Arrowhead, California.
- Stamp-in-the-Box - Blog and Michigan clues and events.
- Letterboxers Anonymous - Forum with clues and discussion topics. Includes helpful hints on methods and supplies.
- Der Mad Stamper - Rubber stamp carver Mitch offers instructions on how to carve a stamp and clues to the many boxes he's planted in the US.
- Fleur de Lis' Letterboxing Journal - Weblog about his letterboxing hobby.
- Rhode Island's Bored Nocturnal Adventurer's Guild - Informal group and clues to the boxes they've planted.
- Mark and Sue Pepe - Couple from Kensington, Connecticut describe activities in eleven states and the island of Aruba.
- LB Con - National letterboxing convention. List of events, tickets and merchandise, accommodations, and visitors guide.
- The Space Traveler - Family offers clues for Pennsylvania, New York and other states.
- Treasure Hikers - Incentive program for letterboxers based on miles hiked.
Media publications
- The Gazette: Letterboxing a Hobby of Inky Fingers and Hidden Treasures - Article on local letterboxing from chain of community newspapers near Washington, DC. (Published 2003-07-09 00:00:00)
- Fox News: Letterboxing Makes Hiking an Adventure - Feature story datelined Oakland, New Jersey. (Published 2002-06-14 00:00:00)
- Washington Post: Thinking Inside the Box - Article by Caroline Kettlewell describes her discovery of the activity. (Published 2002-07-12 00:00:00)
- NPR : Letterboxing - Radio host Linda Wertheimer and Thomas Johnston, an enthusiast in Washington, D.C., find a letterbox near the White House. [audio] (Published 2004-04-10 00:00:00)
- New Times: Carved in Rubber - Introductory article by Ashley Schwellenbach featuring a letterboxer and the founder of Atlas Quest. (Published 2009-06-17 00:00:00)