Today, the established big online communities are accepted and used extensively by broad parts of society. However, the high degree of specialization in professional and private life cannot be addressed by existing online communities for the mass-market. This leads to a need for dedicated online communities which focus on certain topics and needs. For example, a Web 2.0 portal for the medical field would have to include certain restrictions and data protection issues which are not covered by standard communities. Prevalent literature treats online marketing strategies of a company or product in existing social networks. Yet, creating new online communities stays mostly untouched by previous texts. This book addresses this deficit. Creating an active user base is a challenging task, however. Listening to users' needs and applying the right marketing techniques is key in attracting new users and encouraging participation. The book summarizes best practices, proposes new ones and performs a longitudinal case-study and survey. The results are incorporated into a social media marketing plan, all against the background of a real existing web portal for open pediatric dosage information.