Is there market demand (ie some genuine unmet need)? If so, then put up some content and people will eventually come. It may be slow, depending in part on how much content you put up. I know of a site that started as a list of links and grew into a forum. The forum part took over and the resource part is now kind of underserved. I think the forum was better when the resource part was more important to the owner. I also know of forums that spring up spontaneously around good websites because folks want to talk and want to connect. People need a reason to be there to begin with.