If you are interested in the Medieval History and especially in the Byzantine History, this is a good  site:

Byzantine Chronicle  (http://www.byzantium.xronikon.com) The emphasis is on the Byzantine Emperors which are presented in a unique way. A lot of info also about the Byzantine Battles. Again, in a very good presentation. A strong element of the site,  the various maps shown with every emperor and every battle. Don't miss it.