For all of these occasions during Holy Week, consider singing general as well.
Palm or Passion Sunday
A Cheering, Chanting, Dizzy Crowd - Thomas A. Troeger
A Stable Light Is Lighted - Richard Wilbur
Day of Delight and Beauty Unbounded
Maundy Thursday
An Upper Room Did Our Lord Prepare - Fred Pratt Green
God Is Love - Sam Batt OwensO Blest Are They Who in Their Love - Michael Morgan
This Is the Night - Peter Abelard
Good Friday
Hear, O Lord, My Plea for Justice - Michael MorganIn the Cross of Christ I Glory - John Bowring
Lord, Why Have You Forsaken Me - Christopher WebberOn a Barren Hilltop - Christopher L. WebberRejected and Despised - Mary Louise BringleThey Crucified My Lord - African American spiritual
You Are My Refuge, Faithful God - David Gambrell
Easter
There are many song choices for Easter morning as well as the season of Easter.