so far, the best screen capture package i’ve found is recordmydesktop, you can run it from the terminal or you can download a gui, package is named gtk-recordmydesktop, people say it also works on kde.

these two packages can be found in the default ubuntu software sources, so..

sudo apt-get update

then install the two said packages..

sudo apt-get install recordmydesktop gtk-recordmydesktop

the program only outputs in .ogg format, but, you can always convert with mencoder, which, btw, is also available in the default ubuntu repo, i learned this package from another pinoy ubuntu user in the forums.

Ubuntu Forums: Record your desktop with recordmydesktop. 

and so again..

sudo apt-get install mencoder

i think avidemux is a front for mencoder, but, i’m not gonna cover that now, cause avidemux also edits videos, i think it’s too bulky if your gonna user it for video conversion only. so to convert OGGs to AVIs using mencoder, here’s a tiny snippet.

mencoder -idx input.ogg -ovc lavc -oac mp3lame -o output.avi

input.ogg is your source file, and output.avi is your desired the output file.
here’s a detailed guide on how to encode videos using mencoder.