Innocents Corebook – Link to the Amazon page, they provide good discounts and free standard shipping. If you’d like a hardcopy of the Core book, it’s probably the best place to find it. Also comes in DriveThruRPG PDF Flavor. Cheaper, but certainly not a hardcopy.
Mr. Gone’s Character Sheets – White Wolf’s full listing of Mr. Gone’s character sheets, has 1 and 2 page interactive character sheets for Innocents characters, as well as an Innocents-based sheet for Supernatural characters of all stripes. Use these for replacements if your sheet gets worn or lost.
Developmental Psychology – For those of us who like to get into the brains of our characters, or who are just trying to wrap our heads around how kids think, great minds have already spent their lives documenting their observations for us. An interesting read, I’d encourage everyone to at least skim the Child Development sections.
Goosebumps – Wikipedia page for the Goosebumps books series. Extremely simple books designed for young readers with largely similar plots, they still maintained a Horror tone without being crass, dirty, or violent. Good examples of horror for children, and probably where your mind goes first when you think of kids and horror. But it’s important to note the tone of this game is not directed to children, but adults. I’d be lying if I said this game wasn’t in some way inspired by this series, but I want to make sure you don’t expect something like this.
Merits – Full list of merits from basically all of the books. Does not include Innocents merits (boooo) but there’s still plenty there.
Little Fears – The other role-playing game of Childhood Terror that the ST freely admits to taking inspiration from. The original edition is out of print, I’ll see if drivethrurpg doesn’t have a PDF copy for sale, if folks are interested in taking a look at it.