Carl Mack can't help attracting a following. As a mechanical engineer for the King County, Wash., wastewater utility, starting in the late 1980s, he stewed that minorities rarely won internships. So, Mack took over the program, "and the students came," he says.

Mack's recent turn as National Society of Black Engineers executive director has produced the same result: NSBE membership has tripled since he arrived, in 2005, and the free summer engineering camps he has launched have drawn more than 9,500 minority middle and elementary-school students, as young as third-graders.