The following Free Adirondack Chair Plans come from The California Redwood Association. This is a classic Adirondack chair and probably one of the easier designs to pull off. The Adirondack chair picture below links directly to the free PDF file.
This is the project that got me into woodworking in my mid 20’s. The Adirondack chair is such a fantastic project since it is one that anyone can build but it is enough work that not everyone will build one. You can select a variety of different materials and can even get very creative with materials such as skis and cutouts.
Good luck with your own Adirondack chair build!