The United States Geological Survey has a wealth of resources that have proved helpful to me in my interest in mapping environmental data. In combing through the data, I'll often follow a trail of links to related information that seems interesting, and inevitably I find myself at a new subdomain. In fact, the USGS uses nearly 85 different subdomains. In an effort to get a better understanding of what exists and to locate information data more easily in the future, I made a list of them, with titles and descriptions. Pull requests encouraged.
Above image from 3dparks.wr.usgs.gov