recordmydesktop (record desktop sessions to an Ogg-Theora-Vorbis file)

recordMyDesktop produces a file(default out.ogg) that contains a video
and audio recording of a desktop session. It attempts to be easy to
use, yet also effective at it's primary task.

It's suggested that you read the User Guide before using recordMyDesktop.
Online guide: http://recordmydesktop.iovar.org/rug/toc.php