This case study explores the implementation of La Cuna, an online mentoring forum in a small, subject-based professional association, the Seminar for the Acquisition of Latin American Library Materials (SALALM). Designed using the social network software Ning, the forum functioned as an informal learning community for 38 members and was an innovative response to geographical challenges and changing technological skills. Using participation data and a questionnaire to analyze the implementation and development of the hybrid e-mentoring community, this study reveals challenges and benefits that should be considered when managing similar professional development activities. While the forum failed to maintain sustained participation, findings revealed the need to assess professional association member needs regularly and highlighted the importance of continued exploration of online learning tools. Through the description of this project, professional associations and other learning communities will gain insights into the creation and implementation of an online e-mentoring learning community, which will be useful as librarians and groups attempt to meet member professional development needs.