From the Conference Co-Chairs Welcome to the 20th Anniversary of the ACM 2006 Conference on Computer Supported Cooperative Work. The CSCW conference is the premier venue for presenting research and development achievements in the design, introduction, and use of technologies that affect groups, organizations, communities and societies. Although work has been an important area of focus over our 20-year history, technology is increasingly supporting a wide range of recreational and social activities. As more and more people across the globe are able to interact online we are rapidly becoming a community of researchers and developers that attend to all aspects of social life. For this event, the program committee has put together a conference that showcases current work, reflects on accomplishments over the last 20 years, and looks to the future. These Proceedings contain the archival elements of the technical program of this year’s CSCW conference. We are excited to report that Paper submissions increased 25% and Notes submissions increased 13% over 2004 levels. Overall, this represents the highest number of submissions in the history of CSCW. As we hit our 20th Anniversary, this is a testament to the growing interest in CSCW research and the vibrancy of the community. New this year, we will be recognizing the authors of the most outstanding Paper and Notes submissions with awards. For more information about the conference and the full array of participation categories, we encourage you to go to www.cscw2006.org. The success of this conference depends on the financial support we receive from our benefactors and contributors. SMART Technologies and the National Science Foundation supported the Conference this year as 20th Anniversary Benefactors. Additional benefactors include Google, IBM, iCore, and Microsoft. Contributors were InfoSys, Intel, Nokia, SAP, Sun Microsystems, and NECTAR. We hope you enjoy the conference and these proceedings. Pamela Hinds David Martin CSCW 2006 Conference Co-Chair CSCW 2006 Conference Co-Chair Stanford University SMART Technologies Inc.