Don't think of it as "The Talk." This needs to be an ongoing conversation with your kids from babyhood on. Maybe if I tell you how I have talked with my own kids (and patients!), it won't be so intimidating for you!

Books that might be helpful:
Preparing for Adolescence by James Dobson
It's Not the Stork! by Robie H. Harris
Celebrate Your Body (and Its Changes, Too!): The Ultimate Puberty Book for Girls by Sonya Renee Taylor
The Care and Keeping of You: The Body Book for Younger Girls by Valorie Schaefer
Guy Stuff: The Body Book for Boys by Cara Natterson
Good Pictures Bad Pictures: Porn-Proofing Today's Young Kids by Kristen A Jenson and Gail Poyner