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

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

RenPy - Ren'Py is a free and cross-platform visual novel engine that helps you use words, pictures, and...

doopoll - Create live, instant, editable polls effortlessly

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

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.