I am placing this book on my "must read" list.
A short essay that provides a succinct and powerful explanation of the Catholic Church's teaching on contraception can be found here.
A commentary on why the Catholic Church opposes contraception can be found here.
Full text of Humanae Vitae can be found here.
Information on the Benefits of Natural Family Planning can be found here.
For a fresh new look at the issue of contraception, check out the new website, 1FLESH, which is geared toward young adults. You can find the website here.