Via ScienceNewsBlog , the mark of the beast was not originally 666. A 3rd century papyrus scrap (click on the link to see it) from the Oxyrhynchus digs show that an early copy of the Book of Revelation actually held it to be 616 .
The second link explains a bit more about the Greek numerology of the book of the Apocalypse. In Revelation, contemporary political figures being criticized were given a number as a moniker. 616 might refer to Emperor Nero, although there is still some disagreement. .
Far too much information on this topic is available at Wikipedia , which has already been updated to mention the Oxyrhynchus press release.