Quizzes for Pages - Quizzes for Pages is an application to create and share quizzes on your Facebook Page.
Codewell.cc - Improve your HTML and CSS skills by practicing on real world design templates.
Outgrow - Enabling marketers boost conversion with interactive, beautiful & viral quizzes/calculators.
Good Code - Free front end coding challenges
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.
One Degree - The Human Search Engine