Check the following Online Learning Resources Curated by Alison Yang. If you need links to these resources, scroll below. 

• Flipgrid
• Voicethread
• NowComment
• ​Slido

• Padlet
• Screencastify
• Google Forms
• ​Quizizz

• Khan Academy
• TED-Ed
• Open Learn
• ​Oneness Project
• ​Formative

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Is Gamification what you are looking for? Here are 3 easy-to-use resources that need not much extra work: 

Goosechase

Gimkit