The main forums to learn about photopass are generally the Theme Parks forum and the Budget Board. But then, those mainly deal with WDW and you'll end up getting confused b/c they talk about things like pre-purchasing the CD and such (you don't do that with
Disneyland/DCA).
I would love a picture of all of us with some special effects that I have seen (in front of castle with tink in background would be cute!). Does the photographer pick the special effects, or do I?
Tink in the background, floating above with pixie dust and the words about dreams coming true, is a border that you put on the pictures you want to put it on.
The special effects that are added by photopass people are things like Tink sitting in your cupped hands (with appropriate "hey, it's Tinkerbell, sitting in my hands!" facial expression), having a lightsaber duel with Darth Vader, having a sword duel with Captain Hook, pointing in shock at Stitch coming out of the ground or sitting next to you on a bench over at DCA, and some others you can find in other photopass threads.
Along with the photopass book that hydroguy mentioned, there's the CD that I believe Sherry mentioned, too. The CD gives you the high resolution copies of each image they took, and before you order the CD, you can go through on the disneyphotopass.com site and edit those pix. Crop, get closer-in, add borders, add appropriate signatures to pictures you had taken with characters, combine those, etc. Each time you save an edit (say you add a border to one pic, or you crop a pic then add a signature, etc) it saves it as another picture. So if you make 5 separate edits to a picture and save each one, that one picture becomes 6.
With the CD comes the rights to those pictures. You can't sell them, but you can print them as much as you want. Having that right is a pretty big thing, b/c just buying a print does NOT give you the legal right to make copies of it.
Alas you can't get ride photos through photopass; those still have to be bought separately and at great cost.
If anyone wants examples of disneyland/dca photopass pix and various borders, check out my trip report (towards the end, and I don't mind if you just skip straight to the pix, I know I talk a lot!) from Sept 2007 and Dec 2007. Because of a big floopy thing that happened, you might see pix from Sept in the Dec report (it's NOT supposed to work that way, the Sept pix should have been gone by Dec) but with Yuletime borders.