Vibrant communities are critical to the success of software companies, especially when your customers are software developers. A quick scan of the biggest players in the software industry reveals some of the largest and most active online communities on the web: Microsoft’s active .NET community, Mozilla’s open-source initiatives, Sun’s fervent Java developers, and Google’s growing API developers. A strong community built around your products can often be the long term competitive advantage that separates you from your competition.

The same is true to an even greater extent for web sites that are built completely around the idea of "community." In the years that have passed since sites like Wikipedia, Digg, and Flickr have been introduced, many copy cat sites have tried to imitate their success with generally poor results. What did the "originals" do right that enabled them to attract and build their massive followings?

In this article we will take a close look at some of the most successful online communities on the web and dissect what makes each community successful. We will then take those lessons and apply them to practical steps you can use to build a community that matches the quality of the products or ideas it surrounds.