The ACM Special Interest Group on Programing LANguages. From their homepage (http://www.acm.org/sigplan/), their mission is:
To explore programming language concepts and tools focusing on design, implementation and efficient use.
To that end, they sponsor several conferences including
ACM SIGPLAN members receive dead tree copies of the
proceedings to these and other conferences. In
addition, SIGPLAN published the SIGPLAN Notices, an
informal monthly publication which contains a conference
calendar, and several monthly columns.