FotoSketcher - Turn photos to paintings, drawings and sketches. FotoSketcher is a 100% free program to turn your photos into beautiful art, automatically.
DrawPile - Drawpile is a drawing program that lets you share the canvas with other users in real time.
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.
PaintTool SAI - Learn to draw in different ways.
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.
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.