Girls: Sadie, Suki, Samaire (Suh-meer-ah, nickname Sam), Samara, Sabine/Sabina, Sabrina, Sibley, Sidonia, Sierra, Saoirse (Seer-shah, Siersha), Shannah, Seraphina (Sera), Serenity/Serena, Savannah (Vanna/Van), Sidney, Sienna, Scarlett, Summer, Stacey, Silvia/Silvie, Sage, Sara, Sheba, Sirena, Skyler, Sophie, Shiri, Shirley, Sunny, Suri, Sherry, Sawyer, Sable, Satchel, Sade, Selia/Seely, Selwyn (Sel/Win), Selma, Sarina (Sari, Rina), Sasha, Shana, Shaela, Seren, Shauna, Sheila, Shari, Shelby, Sigourney, Shelley, Sibyl, Shiloh, Siobhan (Shiv-vahn), Susannah, Sora, Steffi/Stefania, Soleil, Susette, etc.
Boys: Samson/Samuel, Sawyer, Sebastien/Sebastian, Sanders, Santos/Santo, Santiago, Saul, Saunders, Seamus, Scott, Seth, Shane, Stuart, Stanley, Shin, Silas, Sigmund (Sig), Silvester, Simon, Skip/Skipper (Kip), Slevin, Spencer, Spike, Stephan (Step), Sullivan (Sully, Van), Sven, etc.
Personally, I love Sadie, Scarlett, Sabrina (Brinn), Sullivan, Seth, and Seamus.
Good luck!!