Hormonal Forecaster http://www.hfc.itgo.com/
Chart your fertility to avoid or achieve pregnancy. Also generate personal statistics, and forecast future moods and behaviors.
Natural Family Planning http://www.rho.org/html/cont-nfp.htm
Brief fact sheet outlines the advantages and limitations of natural family planning, also called periodic abstinence, which requires users to practice abstinence during the fertile period of a woman's menstrual cycle.