Outgrow - Enabling marketers boost conversion with interactive, beautiful & viral quizzes/calculators.

Twine - Twine is an open-source tool for telling interactive, nonlinear stories.

doopoll - Create live, instant, editable polls effortlessly

Ink by Inkle - ink is a popular open source scripting language for branching stories, designed for writers

Poll Everywhere - Audience response system that uses mobile phones, twitter, and the web. Responses are displayed in real-time on gorgeous charts in PowerPoint, Keynote, or web browser.

Quest - Quest lets you create sophisticated text-based games, without having to program.