If you are referencing the Proceedings for academic purposes, see below for the appropriate APA formatting.

Proceedings as a whole publication:
Editorial Fellows Team (Eds.). (2012). Proceedings of the International Association for Research on Service-Learning and Community Engagement 12th annual conference. New Orleans, LA: IARSLCE. Retrieved from http://iarslceproceedings2012.wikispaces.com

A specific session page within the Proceedings:
Author(s). (2012). Title of session. In Editorial Fellows Team (Eds.), Proceedings of the International Association for Research on Service-Learning and Community Engagement 12th annual conference. New Orleans, LA: IARSLCE. Retrieved from [URL of specific page]