You can learn a lot about transmedia making from this slideshow.  Robert Pratton of Zen Films presented it at the Sacramento Film Festival a couple of weeks ago.  It has tons of examples of transmedia projects, dissects various business models and offers a process for transmedia creation.  His final examples is a Canadian project that still seems to be in development, Heroes of the North.

View more presentations from Zen Films.

Many thanks to Rob Mills for the link.