Question2Answer - A Q&A site helps an online community to share knowledge.
Pingo - Optimize images for the web quickly 🖼️⚡
Stack Overflow - Community-based Q&A part of the Stack Exchange platform.
Mentimeter - a web-based polling tool for workshops, conferences & events
The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
Imakiku - Imakiku is an audience response system for real-time voting, posting comments, and surveying.