Question2Answer - A Q&A site helps an online community to share knowledge.
Kahoot! - Kahoot! makes it easy to create, play and share fun learning games in minutes—for any subject, in any language, on any device.
Stack Overflow - Community-based Q&A part of the Stack Exchange platform.
Sli.do - Slido is the ultimate Q&A and polling platform for live and virtual meetings and events. It offers interactive Q&A, live polls and insights about your audience.
The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
Mentimeter - a web-based polling tool for workshops, conferences & events