I've come across some websites lately that make me so excited. People have been creating websites, and there's even a tumblr. or two that I've found, that are for a different world. Take, for example, Trask Industries, a website created to defeat the mutant threat of the X-Men.
There's also Capitol Couture, a tumblr. created to showcase the fashion of the Capitol.
Another one I've come across is The Daily Bugle. It's a tumblr. that publishes news articles for the world of Spider-Man.
With all of these, you can get involved in their world. They've gone past interactive journalism and made interactive journalism for fictional worlds. And it's so cool. Let me know if you've found anymore websites like this!