GIMP is the GNU Image Manipulation Program.It is a software similar to Photoshop and has many features which makes it a strong competitor.
Many people and even those in the world of graphic designing have not heard about these tool. This tool is freely available on all major Linux distributions and other operating systems such as Windows. So u might already be having it on u r system.
The official website is at http://www.gimp.org/
I found a tutorial while googling for some gimp help at http://www.troubleshooters.com/linux/gimp/
Will post it here as i find some more….
Meanwhile Happy Gimping!!!!