A BROAD SELECTION of exhibitions opened at art museums throughout the United States over the summer months. A great number of these shows remain on view, some through September, others further into the fall and beyond. Major traveling exhibitions of Bob Thompson, Joseph Yoakum, and Alma Thomas are underway. The first solo museum exhibitions of Caroline Kent and Simphiwe Ndzube are debuting in Chicago and Denver, while the first survey exhibitions of Jamal Cyrus and Jacolby Satterwhite are on view in Houston and Pittsburgh. Jennifer Packer and Cauline Smith have shows, too. In Nashville, a major retrospective of legendary sculptor William Edmondson is being staged, the first such presentation in two decades: