One measure of an idea's brilliance is how obvious it seems in retrospect. For example: the idea that older people can still learn and contribute to society? Well, duh. But when educator Marylen Mann, 68, started espousing this concept in the mid-1970s, it was far from a foregone conclusion. Senior centers in her hometown of St. Louis—and across the country—offered babyish, make-work activities, Mann recalls. In 1982 she and a friend, the late Margie Wolcott May, formed OASIS, an organization dedicated to providing challenging, meaningful pursuits for people over 50. "There was a lot of skepticism about whether the program would work," Mann says now. "Would people really sign up for an eight-week class in creative writing or biblical archaeology, or learn piano at this age? We didn't know." But the response was overwhelming, and the program has since expanded to serve more than 360,000 adults in 26 U.S. cities. Along with low-cost and free courses, OASIS has built an army of almost 6,000 literacy volunteers, who work one-on-one with schoolchildren across the country. And in 2001 the group launched a computer-training curriculum for people reentering the work force after retirement. "Every time we get an idea, people say, 'Do you think people are really going to do this?' " Mann laughs. "We say, 'You just haven't been around OASIS long enough.' "

*The name of this award was originally the Impact Award. In 2008, the awards were renamed as the Inspire Awards.