Thanks everyone for your input. I love that about these boards, you can always count on getting top notch information.
I was able to check out the site and we are probably not going the passport route for our upcoming cruise. There are five of us, and it's almost $400 to get them.
I was actually checking for my 17 year old daughter who will be flying on her own next month to South Carolina to visit family. She doesn't drive yet and doesn't have a student ID. We think we will be okay with a county issued photo ID and her birth certificate. It is never a problem when we fly as a family, because they ID us, but this time she'll be flying solo.
Again, thanks for all of the help!