WikiLearn - learn, teach? both!
WikiLearn is a platform where you can create collaborative learning materials and share it with the world. Since we believe in anonymous collaboration, every material on this platform can be changed by anyone , you don't even need any sort of account. Just click on the Edit button and you can start improving that particular material as you see fit.
As an example of what you can build here, you can look at the following simple task: Multiple-Choice