The Eastern Province of the Domincans here in the states have posted on their web site/blog a talk given by Fr. John Baptist Ku, OP, on how to present the teaching of Humanae Vitae in parish preaching. Fr. Ku delivers the homily that he gives every year on the anniversary of Humanae Vitae in which he challenges the members of his parish to live a life of chastity as we have been called to by Christ.
If you have not read Humanae Vitae, it is a rather short document (especially compared to anything that JPII wrote!) Pope Paul VI has turned out to be rather prophetic in what he wrote about, the link between artificial means of contraception and abortion and widespread use of both as demeaning the theology of sex and the intimacy to be shared by a husband and wife.
The document can be found here, do yourself a favor and take the 15 minutes to read it.