It is only fair that women (and the men they're involved with!) know the facts about the variety of birth control chemicals and devices that are available to them. And that information should include the specific ways in which the drug or device actually works as well as the health risks these things present.
Well, an excellent resource which does just that is available from Concerned Women for America in the form of a handy but relevantly detailed pamphlet. You can read the pamphlet online right here or you can order hard copies to pass around to others at the CWA home page.