Byzantine Studies on the Internet. This site gives access to a great deal of excellent source material, many useful links and information for Byzantine studies.
However, some pages by the author that are linked to it express opinions on theology and sexuality which some people find contentious and offensive.
Dumbarton Oaks Material from the Dumbarton Oaks Research Centre and library, one of the world's top institutions for Byzantine studies.
Graham Sumner is one of Europes pre-eminent historical illustrators. He has done a great deal of work on the earlier Roman Empire, and has illustrated Timothy Dawsons book on the court and military dress of the later empire, By the Emperors Hand. (See the publications page for full details)