Seeing the gimp is the only animal I know for this job... let's try my easy intro to ani-GIF:
Save a copy of my avatar and open with gimp
You will notice this GIF file has two layers (if you don't have this window open, it is under Dialogs/Layers)
The key is to double click on each layer's name and add in the time to display each layer.
My two layers are named "Background" and "Frame 2" which I added
CODE
(700ms)
for the timing element of the animation
Another thing to remember is to convert to indexed color. Do this by selecting "indexed color" under Image/Mode drop menu.
Do a File/ Save As and choose the GIF extension. In the pop-up window, select "Save as Animation" and click the "Export" button.
Click "OK" and you should have an animated GIF.