When DD was 9 we started with the AG book referred to already here, The Care and Keeping of You; BTW it is excellent and I highly recommend it. Whenever it is off her bookshelf I replace it so I know how many times she has read it (she would almost never willingly clean her room so this is how I track her interest

). Also we have had the actual "marriage act" talk recently as she had just "become a woman" for the first time. She was appropriately "grossed out" for an almost 12 yr old. I was very specific and gave her anatomically correct details and terminology. I also told her it was actually very nice when you are with the love of your life (DH).
The whole point my DH had was, "did you tell her the sp*** are microscopic and aren't like little fishes that swim around inside her?" LOL

I had never even thought of that, I guess I need to revisit the "microscopic" version of events. From reading the other posts here it seems I need to tell her the eggs inside her are microscopic as well. Finally, a friend asked me if I had the "oral" talk with her and I said no, but in this day and age I guess I need to do that next... *sigh*
ETA: My products are always around and out and about. DS sees them as well, but has not asked much yet. He does know that a mom and a dad are needed to make a baby. I always talk to DD about bodily changes, health, BO, feelings, hormones and etc so she knows this is ongoing.
Another friend had told her daughter that once you get your period, you are able to get PG and etc. Her daughter took that to mean she would only have her period ONCE in her life. YIKES! Luckily this misunderstanding had been cleared up and her DD has not yet started her "." Can you imagine the SHOCK if she had gotten her period one month and then the next and the next and the next?