Blemder is a Free-to-Use 3D art development program that is widely used throughout game development these days, for its ease of use and advanced toolset.
Daz3D is another great Free-to-Use 3D art development program for modeling, Rendering and Animating. If you are new to 3D art development you might find this system more user-friendly than Blender. Daz3D was used on CAPTAIN AMERICA, THOR and IRON MAN.
Sculptris is a Free-to-Use 3D character and modeling program from Pixologic. This is a great program to dive into if your new to drawing 3D characters and can’t afford more costly solutions. Made by the same developer as ZBrush.
Krita has become one of the leading Free-to-Use 2D art development and photo editing programs out there today. Easy for most to pick up and learn, with many of the same advanced drawing and editing features found in commercial art programs.
GIMP is a cross-platform image editor available for GNU/Linux, OS X, Windows, and more operating systems. It is free software, you can change its source code and distribute your changes.
Whether you are an illustrator, designer, web designer or just someone who needs to create some vector imagery, Inkscape is for you! Inkscape is one of the leading Free-to-Use vector graphics programs out there.
OpenToonz is an Open-Source Animation Production package that is really cool to use if your interested in 2D animations that can be used in games, YouTube and movie film production.