First, you can just go to the very beginning! The archive begins with the middle ages, and you'll quickly run into fun series of strips based on Beowulf and Arthurian Legend. Afterwards, you've got another 600 something strips to keep enjoying.
Lit Brick is a comic started by Jodie Troutman in an effort to read the entire Norton Anthology of English Literature. Having eventually succeeded in that goal, it now features comics about all manner of random literature. For more of Jodie's work, visit troutcave.net!