- Signature Healthcare Brockton Hospital
- Silicon Labs
- Silicon Mountains
- Silicones Environmental Health Safety Council
- Sills Cummis Radin Tischman Epstein andGross
- Siloam Springs Nursing and Rehab
- Siloam Springs Regional Hospital
- Silverado Resort
- Silverado, Annadale
- Silverleaf of Athens, Inc
- Silverliners
- Silvertechnologies
- Simeus Foods International Inc.
- Simmons College
- Simmons Healthcare
- Simmons Manufacturing
- Simply Thick LLC
- Simpson General Hospital
- Sinai Hospital of Baltimore
- Sinai-Grace Hospital
- Sinclair Community College-Phi Theta Kappa
- Singing River Gulfport
- Singing River Hospital
- Sino Television, Inc.
- Sioux Center Health Avera
- Sioux City Fire Rescue
- Sioux County Courthouse
- Sioux Empire United Way, Inc.
- Siouxland Community Health Center
- Sirsi
- Sister Cities International
- Sisters of Charity Hospital
- Sisters of Charity Hospital, St. Joseph Campus
- Sisters of Providence Health Systems- Mercy Medical Center
- Sisters of the Catholic Apostolate Pallottines)
- Sisters, Servants of the IHM
- Sistersville General Hospital
- SITE Group
- Sitescape
- SIU Medicine Springfield Residency Program
- Skagit County
- Skanska USA Building Inc.
- Skidmore Owings and Merrill LLP
- Skiff Medical Center
- Skokie Hospital
- Sky Insurance
- Sky Ridge Medical Center
- Skyline Exhibits-The Holt Group Inc.
- Skywest Airlines
- Slakey Bros.