George Gassaway’s Saturn IB drawings (Start here): http://www.georgesrockets.com/GRP/Preview/Saturn-IB.html
Real Space Models (Great detail!): http://www.realspacemodels.com/drawing-sets/
Hero Relics (so much stuff!): http://heroicrelics.org/index.html
NASA Technical Drawings and Diagrams (not as useful as you’d expect): https://www.hq.nasa.gov/office/pao/History/diagrams/diagrams.htm
Body wraps: http://www.rocketshoppe.com/info/saturn_1b_100/
Photos of static displays (at the bottom of the page): http://www.primeportal.net/photo_home/howard_mason_home.htm
Saturn family: http://www.alternatewars.com/SpaceRace/Saturn/Saturn.htm
Great reference photos: http://mek.kosmo.cz/newware/nw133pho.htm
Photo archive: http://www.apolloarchive.com/
An attempt at an authoritative site: https://www.apollosaturn.com/
Saturn I references: http://meatballrocketry.com/scale-data/
… also some good tips for building: http://meatballrocketry.com/saturn-construction-tips/
A good starting point for any rocket is Peter Alway’s “Rockets of the World”: https://www.amazon.com/Rockets-world-Peter-Alway/dp/0962787671/