Stack Overflow - Community-based Q&A part of the Stack Exchange platform.
Pingo - Optimize images for the web quickly 🖼️⚡
The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
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.
Askalot - Askalot is a next generation CQA (Community Question and Answer) system.
Mentimeter - a web-based polling tool for workshops, conferences & events