Camtasia is a downloadable program. It costs money, but it does have a free trial, for those who are interested in checking it out. It does have some nice editing features, and it has a nice option to use it with PowerPoint presentations.
This tool can be found at: http://www.techsmith.com/camtasia/
Here is a video I made using Camtasia's PowerPoint plug-in:
Screencast-o-matic is a free web-based tool, meaning it does not have to be downloaded. It does not have much in the way of editing options, but it works very nicely as a free product.
You can use this tool at the Screencast-o-matic website.
The screen capture below shows the homepage. Simply click the "Start Recording" button to start making screen capture videos on the web.
The image below shows a comparison between the free version and the version available as a member for $12 per year.
Both Camtasia and Screencast-o-matic can be very useful tools for educators. I have already made some short videos with each of them to use as lessons and tutorials. These tools are definitely worth checking out.