Nonprofit organizations often need to excel in coordinating with other organizations and must do so in a variety of contexts and levels from the informal to the formal. Their ability to accomplish their mission can critically depend on their efficacy in managing dependencies on others for tasks, accessing needed resources, raising their profile in the community, and achieving their goals. Although much research has been done to understand systems for supporting formal coordination between organizations, there is a gap in understanding how informal coordination can be supported by systems. As a first step towards addressing this gap, we conducted a field study of a network of nonprofit organizations, focusing specifically on informal interactions among them. Based on this study, we characterize informal coordination between organizations and the context for such interactions. Our findings point to a need to further explore a class of interorganizational interactions that may not be adequately explored or understood by our research community.