DrawPile - Drawpile is a drawing program that lets you share the canvas with other users in real time.
FotoSketcher - Turn photos to paintings, drawings and sketches. FotoSketcher is a 100% free program to turn your photos into beautiful art, automatically.
PaintTool SAI - Learn to draw in different ways.
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.
Soulver - Soulver is a software application that functions as a calculator that allows you type a continuous stream of information rather than having to input data into multiple cells.