South Bay Mobilization (SBM)

South Carolina Progressive Network (SCPN)

Southern Christian Leadership Conference (SCLC)

Southern Oregon Progressive Network (SOPN)

Southern Poverty Law Center (SPLC)

Southwest Alliance to Resist Militarization (SWARM)

Standing Together to Organize a Revolutionary Movement (STORM)

Stanley Foundation

State Voices (SV)

Steiner-King Foundation (SKF)

Steven and Michele Kirsch Foundation

Stewart R. Mott Foundation

Stop Mass Incarceration Network (SMIN)

Strategic Consulting Group (SCG)

Student Liberation Action Collective (SLAC)

Student Nonviolent Coordinating Committee (SNCC)

Student Peace Action Network (SPAN)

Students and Youth for a New America (SYNA)

Students for a Democratic Society (SDS, founded 1959)

Students for a Democratic Society (SDS, founded 2006)

Students for Justice in Palestine (SJP)

Sunlight Foundation

Sunrise Movement (SM)

Supporters of the Islamic League (SIL)

Surdna Foundation