There are various ways to record your screen while giving a presentation and share that video with others. Many of these programs are online, free or have a nominal cost.
The recommended cross-platform solution at the moment is Google Hangouts on Air. This method works with both Windows and Mac, allows you to record webinars as you give them and is free. It is important to note that currently, with Hangouts on Air, to record a powerpoint presentation successfully you will need to select the “Screen Share” option instead of choosing the powerpoint application.
For a step by step tutorial on how to set up Google Hangouts on Air to record what is displayed on your computer screen, use this guide: http://www.eduhacker.net/technology/google-hangouts-lecture-capture.html
- NB: You will need to have activated youtube for your particular google account you want to use for the instructions at Eduhacker.net to work.