Catechism of the Catholic Church: here.
Compendium of the Social Doctrine of the Church: here.
Vatican Congregations: Congregation for the Doctrine of the Faith // Congregation for Divine Worship and the Discipline of the Sacraments // Congregation for Catholic Education // Congregation for the Causes of Saints // Congregation for the Evangelization of Peoples // Congregation for Clergy // Congregation for Consecrated Life and Societies of Apostolic Life
Pontifical Commissions: Biblical Commission // Commission for Sacred Archaeology // Pontifical Commission for the Cultural Heritage of the Church // Theological Commission
U.S. Bishops: here.
National Catholic Bioethics Center: here.
St. Thomas Aquinas: here.