iShowU is software to capture and record video from your screen into a Quicktime movie in real-time. Create tutorials, make a demo for the Web, record your favorite game, collaborate on UI design, or show tech support what's really going on with that broken program. It allows you to capture and record anything you can see on your screen, along with audio from any compatible source.
ImageIM is a plugin for Gaim that lets buddies send screenshots to each other via HTTP. Users can simply click the ImageIM button, select a portion of the screen, and then send their buddy the image. If the buddy doesn't have ImageIM, they will receive a link pointing them to the image.