http://www.letterboxing.org/, where you can scroll by state, county, and town for letterbox lisings. At http://www.atlasquest.com/, you'll find a far more sophisticated website listing many variations of this intriguing pastime and allowing for the quest of wheelchair accessible letterboxes.
Letterboxes contain stamps on family friendly topics (typically), ranging from cartoon characters, historical tidbits, nature lore, literary references, place-based commemoratives, personal tributes, favorite movies, and more. Clues can be straightforward directions using landmarks, compass readings, stories, riddles, puzzles, images - you name it. Stamps can be made from erasers or artist's carving material, carved by kids or adults, with a full array of styles, sizes, artistic ability. Anyone can make a letterbox, even with a store bought stamp.
I first found out about letterboxing through my work in the state parks. When I realized these boxes were hidden under my nose in familiar places, I was intrigued. When I found my first letterbox, I was hooked. In the 3 years since, carving stamps and questing for letterboxes has inspired new discoveries in familiar places, enhanced my vacations, linked me with a community of friendly people, motivated more hikes, and inspired my personal artwork. If you meet me on the trail, online, or at a DCR Universal Access Program, I go by the trail name Curious Crow.
In developing letterboxing as an accessible element in our recreation programs, I've learned that the teamwork often involved is perfect for enhancing access. People go out as families, couples, buddies, and small groups to find boxes hidden in parks, libraries, stores, cemetaries, mountaintops, urban environments, and other public places. You might have to hike miles to find a box, or just step out of your car. I can hide a letterbox close to the trail, but it still may take an extra pair of hands to reach for the box. By drawing upon people's abilities, everyone in a group ends up contributing to the process of finding the box and enjoying the discovery.
Even if you are unable to leave your house, letterboxing is possible - through the mail! Another variation is letterboxing events. I attended one today at Mt. Tom State Reservation in Holyoke. About 75 people attended Boxing Lake Bray organized on-line by 2 letterboxers, with Children's Fictional Characters as a main theme. Not only were traditional letterboxes hidden around the park, special event stamps were set out on tables for all to access, people exchanged personal stamps, and "cooties" jumped from person to person. In 3 hours, I collected over 100 stamps and met many letterboxers, while sitting! The multiple facets of letterboxing allow for choosing whatever level of engagement you want to have, whether or not you have a disability. Everything you need to know is at Atlas Quest. Check it out!