Screencasts can be very effective ways to communicate. Even a format as simple as a series of images and a voice-over (with or without the annoying background musice) can be powerful
This combination is free and available for Windows and Mac. If you want to add a voice-over to your screencast, you will need a microphone for the computer as well. Of course, you need a quiet room to make the audio. That's it. You are now a big producer! For free!. Remember: there is no privacy on the web. Period. But this is a great tool to have for free.
Here is an excellent quick screencast about Jing and Screencast.com by Peter WebExplorations. Once you have Jing installed, this tutorial will take you through the steps.