1. The Catechism of the Catholic Church (CCC) is the official summary of Church Teachings written in 1992 and slightly amended in 1997. A topical index is found here. A summary was created in the form of the Compendium of the Catholic Church. A non-approved plain language version is also available. A version designed for youth, YouCat is only available in print.
2. The Theology Library from Spring Hill College provides an extensive list of weblinks on various topics in theology and religious education.
3. A comprehensive archive of popular summaries on various Catholic teachings are found in the Catholic Update archive. These have the imprimatur of a Catholic Bishop. American Catholic also publish Scripture from Scratch which, you guessed it, looks at topics arising out of the Bible.
5. Code of Canon Law is the official laws of the Church.
6. Felix Just SJ Catholic Resources for Bible, Liturgy, Art, and Theology