Originally Posted by bigrigdriver
While I will admit that yes, you should Google anything before you post a question about it on a forum, I also think it would be a good idea to at least give an example.
recordMyDesktop is probably a good starting point. You can typically download it from the software repositories (using the package manager on your system, such as Synaptic), and it's fairly easy to use if you get the package with the GTK graphical interface (gtk-recordMyDesktop). The only problem I've found with it is that it's not really good for recording under a compositing window manager (such as Compiz Fusion, if you have it enabled), as it creates tearing, especially with complex animations and/or wobbly windows. Your results may be different, though.
There are others if you look for them. Google really is your friend here.