GIFReadWriter putForm: Display onFileNamed: 'screenshot.GIF'
(The fixes from HansMartinMosner are included in the release.)
The GIFReadWriter class can encode and decode GIF images to Squeak's internal Form format. putForm:onFileNamed: takes a Form and encodes a GIF from it.
Why This is Interesting:
The whole Display is just a Form, actually, it's a DisplayScreen, which is a subclass of Form. You can send the whole thing to GIF, or just a window, or something cool that you draw.
There are also other subclasses of ImageReadWriter.