The domain suffix of a website (the postscript at the end of a web address) can be a good indicator of the the website's authority and accuracy.
"Provides basic intelligence on the history, people, government, economy, energy, geography, environment, communications, transportation, military, terrorism, and transnational issues for 266 world entities."
"An online coursebook suitable for undergraduates introducing the field of Celtic Studies: the various kinds of evidence available about Celtic-speaking communities through over two millennia and the methods available for understanding them."
The Labyrinth: Resources for Medieval Studies
"medieval studies primary and secondary resources from around the world"
Roy Rosenzweig Center for History and New Media
"More than sixty projects, including online resources for teachers; online collections, exhibits and collecting sites; open-source software; and forums to develop knowledge and build community among those in the humanities working with digital technology."
Collection of sketchbooks, drawings, watercolors, rare prints and early photographs.
"An ambitious effort by an international collaboration of scholars to see the world whole, c. 500 to 1500 CE, to deliver the stories of lives, objects, and actions in dynamic relationship and change across deep time."
"Presents detailed and accurate historical maps of several countries in an innovative way"
"Covers the history, literature and culture of the Greco-Roman world"
Prosopography of the Byzantine World
"A project covering the period AD 1025-1180,"