GIMP is a free image editing software like Adobe Photoshop, but they call GIMP an image manipulation program. GIMP works for a lot of operating systems like Mac, Windows and Linux but also FreeBSD and Solaris. I found some video tutorials for GIMP of different quality of course.
One is: “How To Make A Userbar In GIMP” It’s uploaded on Google Video.
You have some quicktime video tutorials on Gimp “Creating a Graduated ND-filter“, “Creating water drops“, “Full flare control” and “LAB color boost“. All video tutorials published at the blog SVDV-Photography.
You also have some video tutorials on GIMP at Designyourownweb.com. Totally 11 tutorials about all from installing GIMP to using Bezier tool, selection tools, transform tool, zoom, move, crop, layers etc.
There are more video tutorials out there. You can point out the more qualitative ones here by doing a blog comment.