Ad Tuendam Fidem: Issued motu proprio by Pope John Paul II on 28 May, 1998. Amends canon law. Preceded by a brief explanation of why this was necessary.
Code of Canon Law: Full text of the 1983 Code, with concordances and word frequency lists. Each chapter in its own file.
College of Cardinals: Information on the men who choose the Pope, including a complete up-to-date list of Cardinals with biographical notes and statistics.
Congregation for the Clergy: Extensive documentation on catechesis (includes the Catechism of the Catholic Church), priests, and deacons.
Ethical and Religious Directives for Catholic Health Care Services: An electronic edition of the guidelines set forth by the United States bishops.
Largest Catholic Communities: Nations and U.S. states with highest numbers of Catholics; nations, U.S. states, and U.S. counties with highest proportion of Catholics; map of Catholic percentage of U.S. states' populations.
Local Catholic Church History and Genealogy Research Guide: For those researching ancestors who were members of the Catholic Church, or who would like to know more about local Catholic history.
Mass Times: Offers Mass times for the U.S. and other countries from information provided by diocese and individual parishes.
New Advent: Besides hosting the Summa Theologica and the 1913 Catholic Encyclopedia, this site offers a Catholic FAQ, selected writings by the Fathers of the Church, and official Church documents, mostly papal, from approximately the last 250 years.
ParishLibraries.com: Why and how to build a multimedia library in your Catholic parish.
Vatican Ecumenical Council I: Decrees of Vatican I. From the Tanner edition. With concordances and word frequency lists.
Vatican Ecumenical Council II: Collection of Vatican II documents. Full text, with concordances and word frequency lists. Each chapter in its own file.
VaticanII.org: Power Search: Allows you to search the Catechism of the Catholic Church, the Catholic Encyclopedia, or the Holy See's web site, all from one page.