Polaroid cameras do still exist. I was thinking of doing something with one myself. It says that the phots they print now are business card sized, so a little smaller than the old version, but at least it would print instantly and then people could sign the back, or stick it in a regular scrapbook and sign the page. Hope that helps!
I would recommend a Fuji instax camera. Polaroids still exist but the film is expensive and the photos don't always come out.
We will be using instax cameras at our reception for a photo booth.
Re: Photo guest book
http://store.polaroid.com/product/9/356223/PIC-300/_/300_Instant_Camera
August 2012 - Married!