(USAtoday.com/AP) At the end of each semester, Bentley College sophomore Shahzad Zia usually offers his used textbooks to the highest bidder on the most popular Internet auction sites. This spring, he plans to list them for a more exclusive community and save money in the process. Zia plans to post his books on College Junktion, an online auction designed by college students, for college students, that opened for business Friday. Registration to the Web site www.collegejunktion.com requires a valid ".edu" e-mail address. Such addresses are reserved for people connected with schools.