Nativeraving: Creating Animated GIF files with Ubuntu 7.10
The section below what what helped me out the most...
Next you need to fire up the GIMP and open the first frame.
Next we need to open all the frames as layers.
To do this we need to go to our first frame and go to the menu:
File>Open as layers
Browse to the folder with all the frames in it and hit CTRL+A
Then hold CTRL and click on your first frame to deselect it and then open the files.
Hit CTRL+L, that will bring up the layers.
To preview your animated image simply go to the picture window then:
Filters>Animation>Playback and hit play.
To help reduce the file size go to:
Filters>Animation>Optimize (for GIF)
All you have to do now is save the image as a GIF and choose to save it as an animation.