Here are the Russian Orthodox saints that start with the letter "S," with their feastdays where available:
- Sabinius, January 30
- Samuel, Martyr in Cilicia, February 16
- Sava the Sanctified, December 5
- Sava, First Archbishop of Serbia, January 12
- Sava of Storozhevsk and Zvenigorod, January 19
- Savvas Nigdelis the Samoladan, November 12
- Savvatius of Solovki, August 8
- Sebastian
- Seleucus, February 16
- Seraphim of Phanarion, December 4
- Seraphim of Sarov, January 2
- Seraphim Rose of Platina
- Serapion of Kozha Lake, June 27
- Serapion the Syndonite, May 14
- Sergius the New Martyr of Petrograd, July 31
- Sergius of Radonezh, September 25
- Sergius of St. Savas Monastery, March 20 and May 16
- Seven Martyred Brothers, January 25
- Seven Virgin Martyrs of Gaza, August 31
- Seven Youths of Ephesus, August 4
- Shemaiah, January 9
- Shio Simeon of Mgvime, May 9
- Siluan of the Far Caves, July 10
- Silvanus of Gaza, October 14
- Silvanus, January 25
- Simeon the Stylite, September 1
- Simeon the Ancient, January 26
- Simeon the Barefoot, April 19
- Simeon of Emesa, July 21
- Simeon the Jeweller, August 14
- Simeon Shio of Mgvime, May 9
- Simeon the Myrrh-Streaming, February 13
- Simeon the New Theologian, March 12
- Simon of the Kiev Caves, May 10
- Simon of Sinai, June 25
- Simon of Yurievets, November 4
- Simon the Zealot, May 4
- Sisoe of the Far Caves, July 6
- Sophia the Martyr
- Sophrony the Anchorite of the Far Caves, May 11
- Sophronius, Patriarch of Jerusalem, March 11
- Spiridon the Proshpora Baker of the Kiev Caves, October 31
- Spyridon the Wonderworker, December 12 and August 11
- Stamatios, January 6
- Stamatios of Volos, August 16
- Stephanis the Martyr
- Stephen of the Kiev Caves, April 27
- Stephen the Savaite, October 28
- Stephen the Bishop of Perm
- Stephen the the Protomartyr Archdeacon
- Stylianos the Hermit, November 26
- Susanna the Martyr
- Susanna of Georgia, also known as Shushannik, October 17
- Susanna the Hierodeaconess, December 15
- Svetlana
- Swithun, January 2
- Sylvester, January 2
- Symeon the Host of God
- Syncletica of Alexandria, January 5
Source: http://www.gnisios.narod.ru/lives.html