On September 28th, the American Museum of Science and Energy will be participating in the Smithsonian Magazine Museum Day Live in which you give your email address and other basic information and request a museum day ticket and it will get you and one other person free admission to a participating museum on September 28th. One ticket per household. If you are not in Oak Ridge, you can find participating museums here.
(My son and I did make it to the AMSE this summer and enjoyed our visit. WE also did the DOE facilities tour and saw a few things we had not seen during the Science Saturday ORNL tour. I have to say I found the flat top house to be incredibly small. I would find it hard to live in that small a space.)