VnTutor has a great post up with 10 Gimp tutorials in video format. Included are:

Gimp Basics
Selective Decolorization
Make a thumping picture in GIMP
Render Images in GIMP
Make a Superkaramba (A-foto) decoration
How to make a banner
Alter an image
Lightning
Retouching a Photo
The User Interface

This looks cool, even for the fairly experienced GIMP user.

Full Story: 10 Gimp Video Lessons Online from VnTutor