- Mayo Clinical Trial Services
- Mayo Regional Hospital
- Maysville Community College
- Mayview State Hospital
- Mazda North American Operations
- MBIA
- MBM Marketing
- MCA Communications Inc.
- McAlester News-Capital and Democrat
- McAlester Public Library
- McAlester Regional Health Center
- McAllen Heart Hospital
- McAllen Medical Center
- McCandlish Holton, PC
- McCollister's Transportation Group
- McCone County
- McCreary Community College
- McCullough Hyde Memorial Hospital - TriHealth
- McCune Foundation
- McCutchen Friends Home
- McDade-Woodcock, Inc.
- McDonough County United Way
- McDonough District Hospital
- McDowell Appalachian Regional Hospital
- McElroy, Deutsch and Mulvaney
- McFarland-Johnson, Inc.
- McGehee Hospital Incorporated (MDCH)
- McGhee Hospital
- McGuffy Industries Inc.
- McGuire Memorial
- McGuire Woods LLP
- McHenry County College
- MCHS - Franciscan Healthcare - La Crosse
- MCHS Franciscan Healthcare
- McKay-Dee Hospital
- McKee Medical Center
- McKenzie County
- McKesson Bio Services
- McKessonHBOC
- McKinley County
- McKinley Marketing Inc.
- McKinney and Company
- McKnight's Long-Term Care News
- McLane Southeast
- McLaren Flint
- McLaren Greater Lansing
- McLaren Macomb
- McLean Cargo Specialists, Inc.
- McLean County Board
- McLennan County Medical Education and Research Foundation