This topic has been discussed at length here:
http://www.flyertalk.com/forum/showt...ferrerid=16109
In summary, other than going to a U.S. embassy, you can get pages added by mail for free, but the time it takes can vary, as you will see from reading the thread.
You have the option to pay for expedited service, which guarantees prompt delivery. I found the free service was too slow, and was able to call, pay for expedited service, and have the passport delivered within a couple of days.