(G) - Indicates a link that is government-owned
(O) - Indicates a link that is an open-sources
(R) - Requires registration
(NA) - Indicates a link that may or may not contain any usable data
(C) - Indicates a link that may contain commercial data
I originally created this mapping with an transportation infrastructure point of view. I would love to include any other resources, especially from fields outside of transportation. Please let me know about anything that might be missing!