Try some popular Medieval Board Games:

Morris or Merrelles* - play online against a friend or the computer here: Online Morris Game

                                  another online version here: Merrelles (Morris)

              * see rules for Morris at wikipedia here: Morris Rules

Fox & Geese* - play against a friend or the computer here: Fox & Geese Online Game

              * see rules for Fox & Geese here: Fox & Geese Rules

If you want to play an actual physical game, print out one of the templates below (you will have to improvise to come up with game board pieces):

Fox and Geese.pdf

goose-game-board.pdf   A game for several players that is played using dice.