Just ran across this - very cool. If you have a copy of Google Earth, you can enable "Trimble Outdoor Trips" which identifies local hiking trails. It does not look like they have the entire AT mapped out, but they do have the PCT and oodles of trails around the AT. It has the route outlined in red and you can click a hiker symbol to get directions for how to get to the trailhead and a brief description of the hike & pictures. The trails seem to be pulled from Backpacker magazine.
Looks like a great resource if you're looking for a new hike in your area or traveling somewhere and want to see if there are any trails in the area.
If you don't have Google Earth, its a free download at earth.google.com. Its a great program if you like maps - just requires an internet connection to work. It also lets you add your own content so I imagine there's a way for the community to add trails that aren't already on there.