| Smithsonian Magazine: They Live and Breathe Letterboxing Abstract of an article by Chris Granstrom, with link to a few references. (April 1, 1998) | |
| Fox News: Letterboxing Makes Hiking an Adventure Feature story datelined Oakland, New Jersey. (June 14, 2002) | |
| Washington Post: Thinking Inside the Box Article by Caroline Kettlewell describes her discovery of the activity. (July 12, 2002) | |
| The Gazette: Letterboxing a Hobby of Inky Fingers and Hidden Treasures Article on local letterboxing from chain of community newspapers near Washington, DC. (July 9, 2003) | |
| 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) | |
| Yahoo! Groups: Letterboxing USA Discussion group for US letterboxers. | |
| Yahoo! Groups: Letterboxing Northeast Discussion group for the northeastern US. | |
| The World of Letterboxing Community Forums and worldwide clues database. | |
| What is Letterboxing? Michelle Spalding offers a history of letterboxing in England and the United States with bibliography. | |
| 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. | |
| Urban Letterboxing Database of clues to letterboxes in urban locations, primarily in Europe. | |
| Twograysquirrels Letterboxes Clues to letterboxes placed by twograysquirrels, mostly in Maryland and Virginia. | |
| 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. | |
| The Space Traveler Family offers clues for Pennsylvania, New York and other states. | |
| Silver Eagle's Letterbox Aerie Clues to nearly 100 letterboxes that Silver Eagle has placed in North America, primarily in Texas. | |
| 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 New York and Pennsylvania. | |
| 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. | |
| Perfect Circle Letterboxing Guild Family and friends offer clues to letterboxes in New Jersey and Pennsylvania. | |
| Oklahoma City Letterboxes by Dennis Williams Clues to boxes in Oklahoma City as well as New Mexico, Alabama, and Costa Rica. | |
| New Zealand Letterboxing Clues, views, and news including boxes from Team Psychokiwi, Judi, Linton, and the Bunny. | |
