- Presbyterian Home of Maryland Inc.
- Prince George's County
- Prince Georges County, Maryland Conference and Visitors Bureau, Inc.
- Princess Royale
- Printis-McCullough and Associates
- Professional Mailing and Distribution Services
- Pulmonary Hypertension Association
- Quality Associates, Inc.
- Quality Inn, Salisbury
- Radio One
- Radisson Hotel Annapolis, Annapolis MD
- Radisson Hotel Cross Key, Baltimore MD
- Radisson Plaza Hotel
- Ramada Inn
- Ramada Inn Rockville, Rockville MD
- RBA - The Retailers Bakery Association
- Realtors Association
- Regulatory Affairs Professionals Society
- Renaissance Cleveland Hotel
- Renaissance Harborplace Hotel
- Reno - Sparks CVB
- Residence Inn by Marriott, Greenbelt, MD
- Respiratory Health Services
- Rocketseed
- Rocky Gap Lodge and Golf Resort, Flintstone, MD
- Roland E. Powell Convention Center
- Royal and Sunalliance
- RS and Mcgladrey
- RWD Technologies
- S-E Management Group, LLC
- Sara Torrence and Associates
- SAS Institute Inc.
- Self Help for Hard of Hearing People, Inc.
- Seton Keough High School
- Seventh Day Adventist Church
- Shadygrove Center
- Sheraton Baltimore North Hotel
- Sheraton Barcelo Hotel Annapolis
- Sheraton Columbia Hotel and Conference Center, Columbia
- Sheraton Inner Harbor Hotel
- Shock Trauma Outpatient Clinic
- Sickle Cell Disease Association of America Inc.
- Sinai Hospital of Baltimore
- Sleep Inn
- SNL Coaching
- Society of Fire Protection Engineers
- Society of Government Travel Professionals
- Southern Maryland Hospital Center
- Springhouse Assisted Living - Silver Spring
- Springhouse Assisted Living -Bethesda