The resources you posted have me salivating, saulgoode. They'll be a major project once the holiday season is over and VL 5.9 goes Gold.
Another Web site with links to GIMP tips and tutorials ishttp://graphicssoft.about.com/b/2007/10/29/gimp-24-released.htm
I have two fairly recent GIMP books. One is Beginning GIMP: From Novice to Professional by Akkana Peck. It's a big book and covers a lot. I haven't started reading and working with it yet. The other is GIMP 2 for Photographers by Klaus Goelker. The book is a series of workshops or tutorials on various Gimp operations and includes a CD with the images used in the tutorials so you can follow along and do the step-by-step exercises. The CD also has a searchable PDF of the book. There is a 2007 book called The Artist's Guide to GIMP Effects by Michael J. Hammel that I haven't seen yet.
There is a companion Web site to that book at http://www.graphics-muse.org/artistsguide/
. It has some tutorials and tips for which you don't need the book.
And of course, there is the GIMP's own Web site at http://www.gimp.org/
that includes links to tutorials and books.
Now if we could just find the time to learn all this stuff...