Byzanz is a command-line/GNOME Panel applet allowing you to record your
current desktop or parts of it to an animated GIF file. This is especially
useful for publishing on the web, since every browser understands the GIF
format.

Byzanz is not limited to gnome, you can use it under non-GTK environments
like KDE too.

Homepage: http://people.freedesktop.org/~company/byzanz/