When Kehilat Hadar met for its first Shabbat morning service on Manhattan's Upper West Side in 2001, about 60 people showed up, some of them spilling into the hallway at the apartment of Ethan Tucker, one of the minyan's founders. Three weeks later the number had ballooned to more than 100. "It was a wide range of people already there and I didn't know half of them," said Rabbi Elie Kaunfer, another of Hadar's three founders. "That's when I actually got a sense that this was bigger than just a couple of friends getting together." Seven years later, Hadar now attracts some 200 worshipers on a typical Shabbat and has a mailing list of about 2,500. More significantly, it has been joined by some 55 so-called independent minyanim across the country. The Jewish institutional world is beginning to take notice. On Monday, representatives of dozens of the minyanim met with academics and communal professionals at Brandeis University for the second independent minyanim conference. The meeting provided a chance to discuss the manifold ways these communities pose both a challenge and an opportunity for established Jewish organizations. "I think ultimately there will be a necessary transformation in what American Judaism and what the institutions of American Jewish life look like in the 21st century," said conference participant Felicia Herman, the executive director of Natan, a foundation that supports several emergent Jewish communities, including independent minyanim. "This is part of that reinvention. We're helping to build a new infrastructure, but we have no idea what it's going to look like." Though the minyanim by nature are independent of the mainstream institutions of Jewish religious life, their rapid growth has made them difficult to ignore. Typically they are lay-led communities with spirited prayer and an ability to attract the elusive cohort of 20- and 30-something Jews that the organized community has struggled to engage in Jewish life. There appears to be widespread agreement that the minyanim provide an avenue of engagement for what sociologists increasingly describe as a new developmental stage: the post-college and pre-marriage period, when many young Jews often fall off the communal radar. Hadar's original Shabbat morning prayer community has spawned Mechon Hadar, an institute creating the first egalitarian yeshiva in the United States to train a corps of leaders for the minyanim, which require highly educated participants for their rabbi-less communities. And while both Kaunfer and Tucker have recently received major grants from Jewish foundations, there has been some hesitation to fund minyanim that are seen as catering to a population that is highly educated and already relatively well-connected to Jewish life. "We felt in the beginning that our added value in the field was focusing on unaffiliated jews," Herman said. "That's changing over time and we've become much more willing to consider organizations that are developing Jewish leaders and that are just giving all kinds of Jews creative new expressions for their Jewish identity." Most minyanim cluster around a point on the ideological spectrum between Orthodox and Conservative Judaism, finding a number of innovative ways to balance an egalitarian impulse with an otherwise traditional prayer service. Most members define themselves as nondenominational, according to survey results presented at the conference. They also seem to reject what several participants refer to as a consumerist model of Judaism, where members pay dues to synagogues in exchange for services provided, in favor of a more participatory experience. But in creating communities with no rabbinic leadership, and where participants are unlikely to affiliate in traditional ways-through synagogue membership, for instance, or by donating to federations-the minyanim pose particular challenges to existing communal structures. Rabbi Sharon Cohen Anisfeld, the dean of the Hebrew College rabbinical school and a longtime member of a Boston-area minyan, joked that by existing communal standards, she probably would be counted as an unaffiliated Jew. "Significant numbers of Jews are rejecting a consumer model of Judaism and opting for a model where they see themselves as co-creators of Jewish life," Cohen Anisfeld said. "In a culture of rampant commodification, this is an amazing achievement." The minyanim also pose significant challenges to the rabbinate. Most of the communities are led by extremely knowledgeable lay leaders who conduct services and deliver Torah commentaries, as well as carry out many of the functions typically performed by rabbis. Even those minyanim that might want a rabbi may find themselves rubbing up against institutions that limit the range of positions their rabbis can assume. "Independence is not compatible with the protectionist guild system that has a stranglehold on the American rabbinate, and I would say on rabbinic creativity," said Tucker, the Hadar co-founder. Though Tucker, speaking in a session on minyanim and rabbinic authority, argued for changes to rabbinic roles and training, he and several others at the conference agreed that no long-term minyan model was viable without some rabbinic guidance. In this respect, as in many others, the minyanim have looked for inspiration to the havurah movement, which saw the rise of similar lay-led and self-governed communities in the 1960s and 1970s. They were sort of a Jewish religious version of the larger countercultural movements of the time. Rabbi Arthur Green, the rector of the Hebrew College rabbinical school and one of the founders of Havurat Shalom in Boston in the late 1960s, said during the closing plenary that a rabbi would have helped havurot avoid another pitfall that threatens the independent minyanim-the tendency toward cliquishness. Green recalled how Havurat Shalom had twice rejected a candidate for membership who had all the qualifications, but was deemed to be a somewhat obnoxious personality who would not get on well with other members. "That was one of my failures of leadership," Green said. "Had I been the rabbi of that group I might have been able to say, 'We stand for something. We're not just here to satisfy ourselves, we're not just here to have fun.' I couldn't do that because I was just one of the group. We didn't believe in professional leadership." Though some of the independent communities are organized around a paid rabbinic leader, most are not, which makes a knowledgeable lay community integral to the continued growth of the minyanim. "The No. 1 scarce resource for the minyanim is not dollars, it's human capital," said Kaunfer, now the executive director of Mechon Hadar. "What's crucial about these communities, it's not a single person who's in charge. It's not even five people. There's a premium on having a wide variety of people running services, teaching, etc. The question is how do you develop that pipeline of participant leaders who can continue to work and grow communities."