May 18 is International Museum Day. The theme this year is "Social Harmony." Visit a local museum today, many are waiving admission fees, but could still use a donation. In New York City, the American Folk Art Museum, the Asia Society and The Frick Collection are offering free admission. The Philadelphia Museum of Art and its historic homes in Fairmount Park are not charging. If you miss out today, there is Museum Day each September, promoted by the Smithsonian.