I’d like to start a bit of reading list of other great resources from around the internet here. Here’s a few to start things off:
##Cambridge in Colour
A classic site with great information. The digital photography tutorials section has many great articles.
##Meet the GIMP
The one stop source of video tutorials from Rolf Steinort, years of tutorials, almost 200, covering many aspects of Gimp and other open source software. The wiki and forum also have some gems of information. Some of the earlier stuff is obsolete now but still interesting, the video’s can be downloaded as torrents, from Youtube or Rolf’s site.
##Strobist
Off-camera lighting theory, examples, and exercises. A wonderful resource for using off-camera flash from photographer David Hobby.
Particularly helpful:
Lighting 101 and Lighting 102.