Web 2 has revolutionized our daily online experience and had a significant impact on the information society. The most important aspect of the Web 2 is that it is social. People are not only the consumer of information; they also actively participate in generating, transforming, enriching, and propagating the information. What makes the Web 2 and social media very powerful is the underlying social structure and communities in every single online service. In this workshop, I will present some of my recent research projects on Social Computing. The core concept of all projects is to build a model to predict the social and collective behavior of users and individuals in a social network or a community. The research projects are from crime index prediction to predicting the direction of stock market movement to applications of machine learning in sport and legal analytics.