Mountainside Medical Center Support Groups. The page lists various hospital support groups open to the public. The “Hospital Support Groups” are professionally-facilitated meetings run by hospital personnel. Please call the telephone numbers listed to learn more. “Community-Based Support Groups” are community-based meetings, not hospital-sponsored meetings. Call ahead to learn if there are any fees to use the resources, and to ensure the support group is still meeting. 1 Bay Avenue, Montclair, NJ. Main number 973-429-6000.