Church volunteers greet visitors entering the lobby. The worship band begins its set and a pastor offers to pray privately with anyone during the service. When the sermon is done, it's time for communion, and the pastor guides attendees through the ritual. Later, worshippers exchange Facebook and e-mail addresses so they can stay in touch. There is nothing remarkable about this encounter, which is replicated countless times each weekend at churches around the world. It's all happening online. The World Wide Web has become the hottest place to build a church. A growing number of congregations are creating Internet offshoots that go far beyond streaming weekly services. The sites are fully interactive, with a dedicated Internet pastor, live...