The Wild Center, is a new Natural History Museum located in Tupper Lake. It has excellent exhibits for all ages. Look at their website for directions.
The Adirondack Center Museum in Elizabethtown, is a history museum focused on Essex County.
The Adirondack Museum is the long-established museum in Blue Mountain Lake that covers the history of all things Adirondack.
Adirondack Park Visitors Interpretive Center in Newcomb run by the State has interesting programs almost daily. A similar center in Paul Smiths is undergoing changes and not open as of May 2011.