Here is a collection of learning resources for Adobe Photoshop, the premier image editing program.
I like the Missing Manual series of books the “Missing Manual†series http://missingmanuals.com/
Peachpit Press has good instuctional books, and video podcasts here http://www.peachpit.com/podcasts/index.aspx
Adobe has the Classroom in a Book series of structured learning http://www.adobe.com/training/books/
Adobe Tutorials http://www.adobe.com/designcenter/
Adobe Support http://www.adobe.com/support/photoshop/
Lynda.com (high quality paid tutorials) http://www.lynda.com/
Good-Tutorials.com http://www.good-tutorials.com/tutorials/photoshop
Tutorialized http://www.tutorialized.com/tutorials/Photoshop/1
Photoshop Tuitorials http://photoshoptutorials.ws/
Photoshop Roadmap http://www.photoshoproadmap.com/Photoshop-tutorials
Keep in mind that there are many resources, and there is no “best” choice because it depends on your learning style which ones will work for you. Also check your local community college, school districts and neighborhood centres, they often have beginners evening classes, if you learn best in a classroom environment.