After the deadly attacks on Sept. 11, 2001, the first person Rabbi Ted Falcon called was his friend, Jamal Rahman, a Sufi imam. On the following Sabbath, the rabbi invited the imam to his Seattle synagogue to speak to the congregation. Soon after, the two spiritual leaders, along with Pastor Don Mackenzie, commenced a series of frank conversations about their beliefs. The talks eventually inspired a radio show, a pair of books, and worldwide speaking tours. The men's willingness to ask and answer tough questions about faith in the wake of 9/11 had clearly struck a nerve with many Americans. Over the past 10 years, the percentage of US congregations involved in interfaith worship has doubled - from 7 to 14 percent. Meanwhile, the percentage of congregations performing interfaith community service nearly tripled - from 8 to almost 21 percent - according to a new survey by Hartford Seminary's Institute for Religion Research. In doing so, these congregations have joined the colorful, decades-old American interfaith movement. Since 9/11, the movement has gained new momentum and, more than ever before, has drawn Muslims into its ranks. "To think about 9/11 without thinking about the interfaith movement would almost be a travesty," says Maureen Fiedler, host of "Interfaith Voices," a ... radio program that was created in the days after the Sept. 11 attacks. "Islam was so misunderstood and so vilified by those events," says Ms. Fiedler, "that a real interfaith understanding has to be brought to bear on the issue."