Is there any more recent translations from the original Latin? I'm basically just looking for the best version out there. I'm mainly concerned with the sections on King Arthur. I've just finished The Discovery of King Arthur by Geoffrey Ashe and wanted to delve more into the source material.
The recent critical edition and translation by Reeve and Wright is pretty great. The facing-page Latin/English may or may not be your ballgame, but I think you'll like the meaty introduction.
I'd also recommend you pick up Christopher Snyder, The World of King Arthur, which is a gorgeous (pictures!) overview of both the sub-Roman Britain in which "the Arthur" is claimed to have lived, and the evolution of the medieval oral tradition and literature that ultimately produced what Snyder argues are really many Arthurs.
Archaeological research on early medieval Britain is currently exploding and also exploding long-held understandings, but for some great reading on the historical setting of a presumed Arthur, check out Robin Fleming, Britain After Rome.
Of course the later medieval Arthur tales are "really" set in a fantasy parallel universe of the time in which they were written. ;) If you're interested in some background reading on that, or some guidance on what to read next in the canon of Arthur literature, let me know!
If you want stuff around King Arthur, then Leslie Alcock's Arthur's Britain: History and Archaeology A.D. 367-634, Guy Halsall's World's of Arthur, and Michael Wood's In Search of Myths and Heroes are all good in either dealing with the literary or historical aspects.