There are currently 5 artists on Last.fm called ST:
1) Aleksandar Stojković ST-vocal of Serbian trip-hop band Goribor
2) ST - Alex Stepanov - russian rapper from Moscow.
3) ST is an abbreviation for the artist Sir Tofur, an electronic/pop artist from the US. He has released one full length, "Like Water, Like Wine, Like Blood, Like Tapestry," and one holiday music EP.
4) Stefan Ternemar (a.k.a. S.T) is an electronic artist from Lidköping, Sweden.
He released his first two EP's Emotions in a Box and I'll Meet You There on the Monotonik label, but has since signed to US indie label Music Related who released his debut album People I Barely