I have created a presentation about open source software, it was a 2.5 hours presentation. You can reuse it from http://www.amadsoft.com/ahm507/Open Source Software.odp

The presentation is in Open Document format, you can open it with Open Office, download and use Open Office from http://www.openoffice.org/. Open Document Format is a standard open format for any office application, read about it on wikipedia http://en.wikipedia.org/wiki/OpenDocument.

The session is followed by an Ubuntu live demo. The primary objective was the introduction of Linux and Ubuntu, Open Source presentation was only a background to understand the value of Open Source operating system.