Many cross-organizational business processes are implemented by hubs and integration platforms which support the electronic collaboration of multiple organizations. The available concepts and solutions based on service-oriented architectures focus on the automatization of long-term business relationships. However, they often do not provide intuitive ways to modify them according to situational needs. In particular, small and medium-sized enterprises characterized by limited know-how and resources are excluded in such electronic collaborations. This paper demonstrates how the user-driven development paradigm of enterprise mashups could be leveraged for implementing cross-organizational business processes. By means of a case study, we report about the experiences of a real-world scenario we have implemented in the frame of the EU-funded research project FAST. A business value analysis highlights the automational, informational and transformational effects. An organized laboratory experiment evaluates how the actual users create enterprise mashups for cross-organizational processes. We conclude with the benefits and limitations of the paradigm.