Ingress Help - Ingress Help with field guides to download and info graphics about all aspects of the scanner, the game, and the Intel map tools, and the social communities around the game.
Ingress Intel Map - The is the official Intel map. A very useful tool to research portals around the globe. Lower level and Unclaimed (Level 0 ) portals are only seen as you zoom in closer to their location.
Smurfling Lessons for Agents - Great work by Agent aymay. These are excellent individual lessons on different parts of Ingress with little pictures/diagrams to go along with them. Things you may not figure out on your own are included here.