Teaching Your Children Healthy Sexuality. I can't say enough good things about this book. Jim Burns' ministry, HomeWord is also worth a look.
Secret Keeper: The Delicate Power of Modesty. There's also a series of fiction books & Bible studies for tween girls and an amazing website for girls and moms (and even a mom blog). Great, great resource.
5 Conversations You Must Have with Your Daughter. Vicky Courtney has been on the front lines of the virtue battle for a while. You can find her website here.
What He Must Be if He Wants to Marry My Daughter. I'm just discovering Voddie Baucham, and am looking forward to learning more about him. This book is a must-have.