Good site for everything Arthur, but particularly original early sources. Complete translations and extracts from the Gallic Chronicles, Nennius, the Annales Cambriae and links to Gildas. Also copies for some of Arthur's disputed genealogies. The only site I've found that makes any attempt to cover the Early British Kingdoms though. Check out Wales, Scotland and the Isle of Man.
Dates are useful.
Originally designed as an aid for those partaking in Role-Playing Games, Kate Monk's investigation has become quite extensive. Includes some epithets too. This site has very quickly become one of the major Arthurian players on the Web. Controversial and thought provoking. Hard facts only to be found here - if you can call Dark Age Records that.