Jenni,
Photopass is a great service that Disney offers. It gives you the opportunity to have every memeber of your party in the pictures. How it works is that throughout the parks Disney has photographers waiting to take your groups picture. With your very first picture they will give you a card that has a barcode specific to your party. Whenever you want any additional pictures taken, you approach the Disney Photographer, hand them your photopass card and they take your picture.
There are some really neat locations where they add special effects such as someone holds their arms like holding a baby and Disney add's baby Simba into that persons arms. There are others with Tink, Stitch...more than I can remember.
It is free to have the Disney Photographers take your picture, however you have to pay to get the pictures printed...and it's not cheap. A lot of people just purchase the Disney Photopass CD which include all of your pictures for $150 which you then can print yourself at home.
There are also individuals who participate in Photopass shares. How this works is that you find other families that are going to Disney around your travel date and you all pitch in to purchase the cd. Once you all return, you upload your pictures and someone burns copies of the cd for each family. This is not allowed through the Dis but you are able to find groups via facebook.
Good luck!