Here is my ten most memorable Folk songs from the 60's in no particular order -

Streets of London - Ralph McTell
Farewell Angelina - Joan Baez
The Lonesome Death of Hattie Carroll - Bob Dylan
Universal Soldier - Buffy St Marie or Donovan
Turn, Turn, Turn - Pete Seeger
Eve of Destruction - Barry McGuire
Woodstock - Joni Mitchell
The Last Thing on my Mind - Tom Paxton
Sound of Silence - Simon and Garfunkel
Dirty Old Town - Ewan McColl

The last song pre-dates the 60's but was first heard by me then and was the first song I learned to play.

There are so many great songs and performers in that decade that this list could be 100 great songs.