Over the years I have collected many pamphlets and booklets that defend the Catholic faith. I was recently sorting through some of these old tracts and I came accross a classic apologetic resource from 'Catholic Answers' entitled Pillar of Fire, Pillar of Truth. It is available online by clicking here. Hard copies can also be ordered from the same site.
'Catholic Answers' is a great resource for apologetics material and for anyone interested in learning more about the Catholic faith. As I read through my copy of Pillar of Fire I thought it would be a good idea to list a few online sources for such apologetics material. Below I've listed a few websites (in no particular order) that explain Church teaching and provide many articles and essays that inform both Catholics and non-Catholics alike:
Catholic Biblical Apologetics
Catholic Education Resource Center
The Nazareth Resource Library
Biblical Evidence for Catholicism
Apologetics Articles (from EWTN)
Fathers of the Church (sorted by doctrine)
Catholic Scriptural Cheat Sheet
Catholic Information & Resources
This list is in no way complete. There are thousands of other websites and blogs dedicated to explaining and defending Catholicism. These are just a few that I have personally used and have found very helpful.