I love JING. It's a screen capture program that is free. Here's one type of use: If a student is absent, you can record a part of a lesson for the student to view later. Here's a sample.

Or, you can make a screencast of you teaching essential items. Here's a sample.

Let me know what you think of these screencasts. I post them in blackboard and the kids use them for studying, catching up, or just to laugh.