Choose Your Own (Twitter) Adventure
Terence Eden is the creator of a creepy, fun story that is modelled after the Choose Your Own Adventure books, and unfolds entirely on Twitter.
You don't need to sign up for Twitter to enjoy it -- here's where you can start Terrence's adventure.
On his blog, Terrence does a great job explaining how he created it.
And here's Inklewriter, the interactive fiction tool Terence mentioned.
Fun Fact! New Choose Your Own Adventure books are still being published - digitally and in print.