This paper presents our research activities on the design of Web 2.0 applications currently ongoing at Politecnico di Milano. Our approaches are based on model-driven development techniques: in particular, they extend Web 1.0 models to cope with the technological characteristics of the new applications and exploit design patterns to capture the desired behaviors. Two main research activities are presented, considering two orthogonal issues of Web 2.0 applications: the social and the technological aspects. Moreover, other ongoing research directions are outlined.