Currently on Kickstarter is the amazing book called ABC: Basic Connections – The Essential Book for Makers from PighiXXX. We have an earlier smaller version of the book and it is a handy reference guide.
Over 200 pages of high quality circuit diagrams and pinouts in easy to understand illustrations. The book is a ring binder so pages can be removed if needed to photocopy or look at more closely.
This book is definitely a step up from the maze of wires you can get with a Fritzing diagram. There will also be a free online component available to backers of the book.