This article details the development of the Library Instruction Wiki (http://instructionwiki.org): an effort to develop a web-based, knowledge-sharing resource. Though some library instruction is specific to a given institution or class, much of what instruction librarians teach is similar. Library instructors have repeatedly expressed the desire to share resources, ideas, and expertise. With the increasing presence of social software applications, the options for technology-enabled knowledge sharing have grown dramatically in recent years. The success of Wikipedia illustrates how wikis can be used to build collective knowledge-building projects. The authors describe the process of using a wiki to build such a resource. Drawing on research connecting communities of practice, information and communication technology, and knowledge management, the authors also examine the social and cultural challenges they faced trying to use communication technology with a dispersed network of practitioners. Implementation details including software selection and installation, customization, and marketing are discussed. A year after its initial launch, contributions to the wiki have slowed despite consistent and enthusiastic support for the concept. The authors examine possible reasons for this limited activity, and suggest next steps for this wiki and for further research. (Contains 1 figure and 23 notes.)