Joe McDonald
Cascades sang the song 'Last Leaf'.
Linoel Richie not sure what year though
I'm looking at the soundtrack CD and no song with that title is in the movie (it's probably a line in a song, and not a song title)
The band The Guess Who originally sang, performed, and recorded the song "Humpty's Blues".
The song is not a 50's song at all. The song was released in 1964 and sang by The Righteous Brothers.
Country Joe McDonald sang "I-Feel-Like-I'm-Fixin'-To-Die Rag" at Woodstock, which is often referred to as the "One two three, what are we fighting for?" song at the festival.
The song, 'I-Feel-Like-I'm-Fixin'-to-Die Rag' was performed by Country Joe and the Fish (lead vocals by Country Joe McDonald).
No song by that name was performed.
No song by that name was played at the original Woodstock in 1969. See the link for a list of all songs played, perhaps the song has a different title.
Country Joe
"Five for Fighting", on their album "Slice".
Woodstock - song - was created in 1969.
Carl Douglas is the artist that sang the song. It was released in 1974. The full title is "Everybody was Kung Fu Fighting."
Adam Gontier from Three Days Grace sang in the song I Don't Care by Apocalyptica.
Danny Hutton
Bob Marley
That song was not played at Woodstock. The entire playlist can be found here: http://en.wikipedia.org/wiki/List_of_performances_and_events_at_Woodstock_Festival