As promised, here are some links to information that I have found helpful in my journey to understanding more about the Church's teaching on contraception, the way the pill works, and NFP. It is most certainly not all there is on the topic and I'll add these links and any future ones I find to my sidebar.
I would recommend that anyone who is beginning to research these topics start with the Janet Smith speech (or see link below to get a free CD version), Contraception, Why Not as well as Pope John Paul II's Humanae Vitae.
Free copy of Contraception, Why Not by Janet Smith. Be warned...it will change your life!
Church's teaching on birth control: Catholic Answers
One More Soul
Questions and Answers about the Pill and more on how it works as an abortifacient