This may come as a surprise to some of you, being that he's dead, but one of my favorite people on the internet is Geoffrey Chaucer. For a dead guy, he's remarkably prolific, maintaining both a blog, and a twitter feed.
Middle English can look intimidating to a modern eye, but this current incarnation of Chaucer is as comfortable with modern culture as he is with modern technology. He has interviewed Margaret Atwood and also considered a "fyne book of sparklie vampyres." On twitter, he makes references to Doctor Who and translates song lyrics from our era into the language of his. He makes Middle English literature much less intimidating, and a great deal of fun.
Then there is professor and writer Michael Livingston, who has translated modern authors such as Doctor Seuss, Mary Robinette Kowal, and John Scalzi into Middle English, and made recordings of these translations. I particularly enjoy his editorial comments on how he converted modern metaphors and idioms into medieval ones - this is really smart, fun stuff.
If you have favorite medieval and modern mashups, geeky or otherwise, please feel free to share them in the comments.