I know this is early, but I wanted to give you advanced notice in case you want to take advantage of this. This may be a good time to take a road trip and head to a different part of the state to visit a museum you wouldn't normally go to.
This is a national thing, but I've listed the locations in Arizona below. Smithsonian Magazine is sponsoring free museum day on Saturday, September 29th. You can print the required ticket and find out more about each museum that's participating at the link above. Unfortunately, the ticket is only good for two people and there is a limit of one per household. Click on any museum below to get a description of what they offer.