I am sure you have heard the popular saying - "A picture is worth a thousand words". It is always nice to have a medium to show people how a particular task is done. And instead of explaining it through words if we can show it in a dynamic form such as a video or a screencast, it will be better received.
Linux has got a couple of tools which aid one in creating screencasts in a number of formats including flash (swf) and mpeg.
One such tool is 'pyvnc2swf' which can be used effectively with the aid of a vnc server to create screencasts in flash or mpeg video. The site wolphination gives a detailed description of how to set up 'pyvnc2swf' to grab screen shots of the desktop to create flash movies of the same. But one thing that has to be noted though is that since this involves the use of a vnc server, it is important to set a password to connect to the vnc server as other wise, anybody with network access to your computer will be able to easily view and control your desktop.
If you are using 'x11vnc', you can create a password file by running :
and then start the vnc server as follows:
# x11vnc -storepassword "password" /path/to/passwordfile
# x11vnc -rfbauth /path/to/passwordfile
Another tool (not necessarily GPLed but free nevertheless) which I have enjoyed using is Wink. This software has to be downloaded from their website and once downloaded and unpacked, just double-clicking on the wink executable script installer.sh will start the installation. And once installed, you can start creating screencast of the whole desktop, a part of the desktop or just an application. There are options for inserting balloons or call-outs giving details of the steps in-between frames. I really enjoyed using this application and surprisingly, the resulting flash file of the screencast was within the acceptable limits which makes it an ideal tool for creating presentations and visual tutorials for publishing on the web. Unfortunately, the Linux version of Wink (1.5) is a bit behind the Windows version (2.0).
A third option which could hold a lot of promise in the future is a software called Istanbul which could well be integrated in the next version of Gnome. This is a python script which when once started will reside in the Gnome taskbar and one can use it effectively to create a video of the going-ons on the desktop.
So we Linux users do have a number of options for creating screencasts though each one of these lack the desired polish and can't be compared in the same league as those found in say OSX for instance. But work on that end is progressing in the right direction as the above projects would prove and we can look forward to a more polished and better integrated experience in the near future.