These days, many prospective college students find the study of gray water as intriguing as gray matter, leading them to select a college based heavily on its environmental sustainability. To assist these green-conscious students, the 2009 Kaplan College Guide for the first time has ranked the top 25 green private and public colleges and universities for efforts in and out of the classroom. Among those on the list are Carnegie Mellon, Dartmouth, Duke, Harvard, MIT, and Yale. "We're offering objective information to students who want to be better global citizens," says Jason Palmer, contributing editor of the 792-page guide.

—Chris A. Weber