MAking animated GIFS

Hey everyone. Can someone please tell me how you can make animated GIF pictures using the screenshots from GW? For example, if i take 20 screenshots REALLY fast one after the other, how can i put them all together so it will look like its moving? Thanks in advance.

http://www.gimp.org/

Look for the GIMP Animation Package (GAP).

Rather good, considering it's open source.