J.H.
Be wary of the black and blue cohosh that other posters have recommended. It can have some very undesirable effects, and can be very dangerous. Same with castor oil, to a lesser degree of dangerousness.
You probably didn't mean it to sound this way, but you said that your first was very healthy and almost 9 pounds, and you definitely don't want that to happen again. I would think you WOULD want that to happen again; a healthy baby is a great thing! And, his weight was very normal. Honestly, women can deliver a five pound baby and have a more difficult labor and birth than someone birthing a 10 pound baby. The weight is not what is important; it's the position of the baby. The suggestion of using a birth/exercise ball is great, not only for helping your body get ready for labor but for encouraging your baby to be in the correct position. If he/she is in the correct position, labor will progress more rapidly and be less painful.
Due dates are very misleading things...the average length of pregnancy for a first time mom is 8 days past the 40 weeks that we've grown accustomed to thinking of as our "due" date. For subsequent births, it's 40 weeks and three days. Your baby will come when he/she is ready, and if you let him/her decide that chances are much higher that you'll actually have a less painful, safer, and easier labor and birth than you would if you were artificially induced before your baby is ready.
Things you can do to encourage labor to start naturally (these things will only work if your body and baby are ready anyway) are walking, using the exercise ball and making wide circles on it, sex, nipple stimulation (although this can produce overly strong contractions and I don't recommend it until you are already in labor and want to strengthen the contractions), Red Raspberry Leaf tea, evening primrose oil, RELAXING is really important (try getting a massage - I can recommend someone if you need), acupuncture, eating pineapple, eating spicy foods, ....
Hope that helps:-)