Appalachian Trail Conservancy
They are a "volunteer-based, private nonprofit organization dedicated to the conservation of the 2,175-mile Appalachian National Scenic Trail, a 250,000-acre greenway extending from Maine to Georgia."  Formerly known as the "Appalachian Trail Conference," they are an 80 year old organization that works with the National Park Service Appalachian Trail Park Office, 30 maintaining clubs and multiple other partners in maintaining the Appalachian Trail.

White Blaze.Net
"A Community of Appalachian Trail Enthusiasts."  This site contains numerous forums concerning hiking and the Appalachian Trail.  Great resource, especially if you're considering a thru-hike.

Tennessee Eastman Hiking and Canoeing Club
We often work collaboratively with Tennessee Eastman in maintaining their section of the Appalachian Trail.  They provide us with tools, instruction, and fellow trail maintainers, and we all go out and give back to the community by maintaining or building new trail.

Mountains to Sea Trail
This trail is going to be awesome once it's completed.  In the fall of 2005, ASU Trail Crew joined a Mountains to Sea maintenance crew to help build brand new trail. 

Mast General Store in Boone
The Mast General Store in Boone has been very supportive of our club and you should check them out.