K. Jonas Nordby -- a runologist doing his PhD research at the University of Oslo -- has cracked the jötunvillur code, a secret rune code used by Vikings in the 13th century. He has been able to decipher 80 Norse inscriptions, including a romantic message that says "Kiss me".
The rest of the rune codes contain no major revelations, according to Nordby: "We have little reason to believe that rune codes should hide sensitive messages, people often wrote short everyday messages." Imagine that: Vikings sending each other love messages before going on their daily pillaging through the coasts of Europe.
The key for the discovery was a 13th century stick that contained the names of two Vikings written in both standard and encoded runes: Sigurd and Lavrans. According to Mediavalists.net, the code "replaces the original runic character with the last sound of the rune name. For example, the rune for 'f', pronounced fe, would be turned into an 'e', while the rune for 'k', pronounced kaun, became 'n'."
You can read more about it an article published in the International Journal of Runic Studies (in PDF).