The Assassin’s Creed (video game) series is an ideal example of storytelling across multiple mediums. Much of what Assassin’s Creed exemplifies can be seen within the realm of most popular video game series. Done, somewhat crudely, to monetize the proliferation of the game’s fictive universe; the series’ lore extends to graphic novels, printed compendiums, fan films, feature films, wikis, spin-off titles, and social media. Similar to much of media, this highly explored universe anchors itself within the mainline series of games; its ancillary works serve to flesh out the history and setting. This may not be the most contemporary or new media approach to cross mediated story, but I think it is a worthy example.
This should have the sufficient links within the website itself: