If you're the one who has to explain computer things to co-workers, friends, or family members, IORAD knows your pain. The webapp is set up specifically to capture screens and video demonstrations, then annotate them with easy-to-grasp tools.
You can either capture a single window and annotate it with text, arrows, and other common image editing tools, or grab a video of everything you do inside a window to demonstrate mouse actions or multi-step processes. When you're done clicking about, IORAD automatically adds arrow pointers and highlights to provide a template for explaining what just went down. It might take a few minutes to get used to the interface, but it's probably a long-term time saver over laborious screen capture and manual image editing.
IORAD is, while in beta, a free tool that requires a sign-up and a Java plug-in.