If you like/use the GIMP (GNU Image Manipulation Program), you might want to check out the free GIMP Magazine at:
http://gimpmagazine.org/
Available to download as a free PDF (59.8MB)or you can buy the magazine on paper if you prefer 
Currently on issue #3 … but back issues are also available.
There’s also GIMP resources, courses, and even a gift shop
and a “GIMP vs PS Comparison Whitepaper”