Here you can see a list of various FREE art programs that can be found on the web. This is by no means a complete list, this simply features the ones that I consider to be worth taking a look at.
If you know a program that should be added to the list, feel free to leave a comment. But remember, it has to be a free program, not a time-limited trial. Feature-limited starter versions are okay.
Update: 22.04.2012
PAINTING PROGRAMS
--------------------------------------
MyPaint
Krita (NOTE - Windows version is highly experimental)
Artweaver
Art Rage (starter edition)
Open canvas 1.1
PHOTO MANIPULATORS
--------------------------------------
GIMP 2.67
Paint.net (NOTE - no pressure sensitivity)
3D
--------------------------------------
Blender
Google Sketchup
Terragen Classic
Terragen 2 (Free Edition)
DAZ STUDIO PRO
BRYCE 7 PRO
HEXAGON
Sculptris
WEB-BASED
Note - might require registration on the website
--------------------------------------
Aviary:
An online set of programs
* Peacock
* Phoenix
* Raven
Sumo paint
dA Muro
Sketcher
MISC
--------------------------------------
Inkscape (vector)
Apophysis ( fractals)
Alchemy
Pencil (animation)