Intel Map (intel.ingress.com) is a website to browse the global Ingress map - not limited by the visual range of the Scanner. The Intel Map can also be used to redeem Passcodes, and is useful for copy-pasting Passcodes on a computer and for iPhone users.
IITC[]
IITC (Ingress Intel Total Conversion, iitc.app) is a set of third-party add-ons for Intel Map that provides additional features on top of the original Intel Map. However, many features require meta-add-ons, and link drawing is not as quick.
While IITC is a modification of official Ingress tools and probably goes against the Terms of Service, there appears to be a silent acceptance by Niantic. Reportedly, following a user campaign in 2014, no agents are known to have been banned due to the use of IITC.[1]
IITC is considered indispensable by players located in China, as local mapping regulations (see Wikipedia: GCJ-02) causes the Intel Map's base Map layer to be shifted relative to real-life Portal locations.
(The original IITC project is located at iitc.me. As it has not released any new version since 2015, the new fork, "IITC Community Edition" at iitc.app, has mostly replaced it.)