I started to look after GIMP tutorials on the web and build a list.

A starter:

Topmost:

GIMP: www.gimp.org/docs or manual.gimp.org/index.html

Tutorials:

GIMP Tutorials Pointer Page 1: www.sai.msu.su/~megera/gimp/schlecht
(a lot old outdated links).

GIMP Tutorials Pointer Page 2: www.xach.com/gimp/tutorials
(mostly books, outdated links)

GIMPology: gimpology.com

GIMP tutorials; www.tigert.com/gimp/tutorials

Books (Online):

Grokking the GIMP: gimp-savvy.com/BOOK

Books:

Amazon DE COM

Beginning GIMP: gimpbook.com/links.html

Links to GIMP Books: www.tigert.com/gimp/books

Other links:

www.tigert.com/gimp