What It Scores
SOS is a valid word in the tournament list this site uses. Tile values only, before any premium square: 3 in Scrabble, 3 in Words With Friends, 3 in Wordfeud. The letters break down as S1 O1 S1.
Words Made From The Letters In SOS
2 shorter words come out of these tiles. On a board that matters more than the long play, because a short word on a premium square often beats a long one on plain squares.
2 letter words (2)
Longer Words Containing SOS
SOS appears inside each of these, which is what makes it worth knowing as a hook.
Next: the Word Unscrambler for any letters at all, and the two and three letter lists. Full entry and definition at Merriam-Webster.