Online screen recorders require Java 1.5 and a supported web-browser:

Freeware based video screen recorder. It allows you to create a screencast of a specific region of your desktop or a full-screen screencast. Screencast-o-Matic can record video with audio. You can also add notes to your screencast at specific times. Also allows to add visual hints to your screencast: the cursor size can be increased and mouse clicks can be highlighted with a circle (to make it easier for people to follow the mouse).Screencast-o-Matic is using a Java applet (requires Java) to do the screen capture and playback so theoretically it should support all major platforms and browsers. The max length of a screencast is limited by 10minutes if you upload the video to YouTube.

Screen capture software for Linux