Ubuntu Linux Pro Graphics Suite - Free

Ubuntu 12.10+ (includes GIMP 2.8+)

Photography: Gimp 2.8+ (included with Ubuntu 12.10)

Vector Illustration: Inkscape 0.48+

Hint: in Ubuntu Software Centre, search for 'inkscape' and install

Advanced (3D Graphics): Blender 2.64+

Hint: in Ubuntu Software Centre, search for 'blender' and install

Layout and eBook: Scribus 1.4+

Hint: in Ubuntu Software Centre, search for 'scribus' and install

Resources and Tutorials

Gimp: gimp.org/docs/, gimpmagazine.org/resources/
Inkscape: inkscapeforum.com/viewtopic.php?f=11&t=2, inkscape.org/doc/
Blender: blender.org/education-help/
Scribus: wiki.scribus.net/canvas/Scribus_Links