The hallmark of the Smithsonian museums is that they're free to the public. In that spirit, Smithsonian Magazine is sponsoring a free day for museums all over the country, and a number of Chicago area museums are participating. In our fair city, the big participating museums are the Adler, the Art Institute and the Museum of Contemporary Art. There are more than 30 museums participating in Illinois. Sign up for tickets on the Smithsonian Magazine website. One ticket is good for two people at one museum.