Saint John XXIII Pope
The Archdiocesan Office for Youth have an excellent and detailed biography of Saint John XXIII. Section One contains information on his virtues while Section Two looks at St John XXIII call to renew and update the Church in Christian unity through the Second Vatican Council. American Catholic has an excellent brief biography of Saint John XXIII. It includes John's own assessment of how he could become a saint. You could also look at the topic of Vatican II in this module for several biographies and/or assessments of the life and work of this great 20th Century Pope.
Church History
The Church History section of RESource assists Religious Education teachers to find reliable online resources in the study of Church History.