Timebanking and volunteering in local nonprofits are major extant paradigms for citizen cooperation, civic contribution, and community building. Both paradigms are currently growing rapidly worldwide. In this paper, we review and analyze key challenges in timebanking and nonprofit volunteering. We argue that both paradigms could benefit from an integrated information infrastructure for volunteering interactions. We validated and developed this design concept through a scenario probe study, and through discussions with timebanks and other nonprofit organizations. We illustrate our design and its rationale through a walkthrough of screen shot mock-ups. Finally, we identify and discuss design issues and future research steps.