On YouTube, the wildly popular video-sharing site, the most-watched video clips include David Letterman's public evisceration of Paris Hilton, music videos by Rihanna and Soulja Boy, and, of course, a young man's heartfelt plea to "leave Britney alone." But YouTube's ocean of clips — some of them trivial, offensive or just bizarre — now find themselves competing with a Web site from a higher authority — GodTube. GodTube, the Christian response to YouTube, is the fastest-growing Web site on the Internet, and the site's top videos reveal a community that couldn't be more different than YouTube's. There are music videos,...