US National Archives
Nara: Charters of Freedom: Slavery and American Revolution: Voices of Protest
Primary source material includes Quaker petition to Congress, October 4, 1783 and Elizabeth "Mumbet" Freeman, watercolor (reproduction) by Susan Anne Livingston Ridley Sedgwick, 1811. Brief informational text.
PBS
Africans in America: Founding of the Pennsylvania Abolition Society
A detailed account of the founding of the first Quaker abolitionist society in 1775 in Philadelphia by Anthony Benezet. The society became known as "PAS" or "Pennsylvania Abolition Society".
Learning to Give
Learning to Give: Anthony Benezet
A detailed biography of the famous Quaker abolitionist who founded the first anti-slave group in Philadelphia in 1772.