This study focuses on upper secondary and vocational level teachers as users of social software i.e. what software they use during their leisure and work and for what purposes they use software in teaching. The study is theorised within a technological pedagogical content knowledge framework, the emphasis is especially on technological knowledge and technological pedagogical knowledge. Four hundred thirty seven teachers were surveyed using an online questionnaire with Likert scaled statements and open-ended questions. Results suggest that the number of different types of social software actively used for teaching is small and that the potential of social software as a tool for supporting collaborative learning has not yet been realised. Discussion of the results is framed in the context of teachers' developing technological pedagogical content knowledge.