Social networking is more and more considered as crucial for helping organizations harness the value of informal relationships and weak ties, without compromising the consolidated business practices embedded in conventional BPM solutions. However, no appropriate notation has been devised for specifying social aspects within business process models. In this paper we propose a first attempt towards the extension of business process notations with social features. In particular, we devise an extension of the BPMN notation for capturing social requirements. Such extension does not alter the semantics of the language: it includes a set of new event types and task types, together with some annotation for the pool/lane levels. This notation enables the description of social behaviours within BPMN diagrams. To demonstrate the applicability of the notation, we implement it within the WebRatio BPM editor and we provide a code generation framework that automatically produces a process enactment Web application connected with mainstream social platforms.