Drawpile

Drawpile is an interesting tool that lets you use your imagination and draw on a blank canvas that's shared with your friends. The application lets several people access the same canvas, so everyone can simultaneously draw on it in real time.

Below the drawing area, there's a chat where you can talk with the other users and decide what to draw together. It includes a series of customizable brushes and settings that provide you with the tools to draw almost anything you can imagine.

You can add multiple layers if you need to, and modify other people's changes. You can also save the steps of the changes you make, so you can see them later or show them to the rest of your friends. This is a really useful option when your friends want to know how you made certain changes to the project.