This Digital archive was funded by the School of Advanced Study to put online the papers of South African anti-apartheid activist Ruth First who was assassinated in 1982. They include letters from her exile in London, political activities in South Africa and Mozambique during the apartheid era and responses to her impact.
Also relevant here are the digitised political pamphlets from the collections of Senate House Library which includes: Exposure! The farm labour scandal by Ruth First (Johannesburg: Real Print. and Pub. Co., 1959).
Likewise SAHistory.org is a great site with timelines, biographies and digitised primary source materials. It has copies of Fighting Talk. which Ruth First edited in the 1950s and contains many examples examples of South African resistance.