If you are familiar with Camstasia and Jing software, you may like Screencast-O-matic software more to record your slide presentation, your speech, and your own teaching. Camtasia is a licence software; it is bulky and has to be installed into your PC. Although you can use a trial version for one month, you have to install it again and again after it expiry date. Camtasia can record your speech or teaching as long as you want. On the other hand, Jing can only record your presentation for 9 minutes.
Screencast-O-matic has more options: you can record your presentation online without installing the software in your PC. That will save some space in your hard disk. Screencast-O-matic allows you to record the presentation for 15 minutes. The recorded video can be saved in many formats, and later be uploaded into YouTube.
Yuou can also watch a few videos from YouTube to learn how to use this tool.