Welcome to the Mega-List!! ^_^
First off, here are some free art programs!;
Photoshop CS2 - (Windows)
FireAlpaca - (Windows and Mac)
Medibang Paint Pro- (windows and Mac)
Autodesk Sketchbook- (windows)Sketchbook Copic Edition - (Windows and Mac)
GIMP - (Windows) (Mac)
Paint tool SAI 2 beta - (tumblr post on said program)Paint tool sai cracked- (Windows and mac)SumoPaint- (here)
iPaint - (Mac)
Paintbrush - (Mac)
Pencil - (Windows, Mac)Paint.NET - (Windows)
Seashore [still in development, ver 0.5] - (Mac)
ChocoFlop - (Mac)
Inkscape - (Mac and Windows)
ArtRage [Demo] - (Mac and Windows)
OpenCanvas 1.1[must pay for 2.0] - (Windows, not sure abo