Congregation for the Doctrine of the Faith. 
Considerations Regarding Proposals to Give Legal Recognitions to Unions Between Homosexual Persons:
http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_20030731_homosexual-unions_en.htmlTopic headings include: the nature of marriage and its inalienable characteristics, statements on the problem of homosexual unions, arguments from reason against legal recognition of homosexual unions, and positions of Catholic politicians with regard to legislation in favor of homosexual unions.
Family, Marriage and “De facto Unions” November 21, 2000.
http://www.vatican.va/roman_curia/pontifical_councils/family/documents/rc_pc_family_doc_20001109_de-facto-unions_en.htmlOffers useful guidelines to pastors in urging politicians and lawmakers to protect the dignity and rights of the family based on marriage. Responds to attempts to grant legal status to “de facto” unions.
US BISHOPS’ STATEMENTS
All citations are from the United States Conference of Catholic Bishops (USCCB) at http://www.usccb.org/
Marriage: Love and Life in the Divine Plan. November, 2009.
http://www.usccb.org/issues-and-action/marriage-and-family/marriage/love-and-life/In this pastoral letter the U.S. Bishops explain key points about the Church’s teaching on marriage. Available in English and Spanish. Abridged version also available.
Between Man and Woman: Questions and Answers about Marriage and Same-Sex Unions, November, 2003.:
http://www.usccb.org/issues-and-action/marriage-and-family/marriage/promotion-and-defense-of-marriage/questions-and-answers-about-marriage-and-same-sex-unions.cfmA cogent summary of church teaching on marriage between a man and woman based on Scripture and tradition. Available in English and Spanish.
Married Love and the Gift of Life, November 14, 2006.
http://nccbuscc.org/laity/marriage/MarriedLove.pdfResponds to questions about married love and contraception. Provides a solid review of Natural Family Planning for engaged and married couples.
Always Our Children: A Pastoral Message to Parents of Homosexual Children and Suggestions for Pastoral Ministers, 1997.
http://www.usccb.org/issues-andaction/human-life-and-dignity/homosexuality/always-our-children.cfmA compassionate response to families struggling with the homosexuality of a loved one. Available in English and Spanish.