Web 2.0 aims to support human interactions and content creation by combining information from different contributors. It can enhance business processes by improving communication, collaboration and exchange of knowledge between various participants. These benefits led to the emergence of a new form of business processes called Social Business Process (SBP). This paper provides for SBP modelling by proposing a domain-specific language (DSL) based on an extension of the standard BPMN notation to model social elements within an SBP. It is simple and yet generic thanks to the reduced number of extensions and its ability to model SBP regardless of the used Web 2.0 technology. To show the applicability of the proposed notation, we have implemented it within the BPMN2 modeller editor.