You might want to take a look at tried-and-tested communities and social networks. Depending on
1. the size of the community
2. your target group
3. the tools you want to provide to the community members
4. whether you want to build an own community site, integrate a community into your site or just establish a community in any social network
5. and the product/business you to build it around,
there is a wide array of other options for building a strong community. Here are some of them:
Pages and Groups can be used as a way to form and organize a community. Attracting users is easy, because you are building the community where most of them go everyday anyway.
Depending on the number of users and the release date of your community, Quora can be called one of the most powerful community platforms. The best thing about it: Quora knows best how to organize information, which makes it perfect for support issues. There are few companies that handle the distribution of relevant information better than Quora.
A great white-label solution, which fits you best, if you already have a website with content set up for the product. It's only the start of a community, though: Disqus focuses on organizing comments.