Here's a list of some of the most popular industry groups on LinkedIn. To join a LinkedIn group, you must have an account on the site. Membership in any group is at the discretion of the group administrator.

-Event Management
-Event Peeps: For Live Event Industry Professionals
-Event Planning & Management
-Financial & Insurance Conference Planners (FICP)
-Meeting & Conference Planners International
-The Meetings Community (MeCo) Group
-Meeting Professionals International (MPI)
-National Business Travel Association (NBTA) NBTA Strategic Meetings Management Programs (SMMP) A sub group of NBTA geared specifically to topics relating to strategic meetings management programs
-Pharmaceutical Meeting Planners
-Professional Convention Management Association (PCMA) ­ Official Group
-SPIN: Senior Planners Industry Network Only meeting planners with at least eight years of direct planning experience are invited to join this group.
-Suppliers with a CMM designation may also join.
-T&E Plus
A group for leaders of SMMPs, procurement, conference planning, and other related departments to share best practices regarding travel and entertainment expense management - Rachel Eccles