I've personally done talks and lectures on Linux at my university. You need to be careful of the audience, if they're a selection of master's level computer scientists you can presume a bit of knowledge, otherwise you need to start by explaining what an operating system is, as most people have no idea. Then introduce the history of GNU (starting well before Linux was created) and then Linux (with perhaps a mention of MINIX by Andrew S. Tanenbaum - the OS that inspired Torvalds to create Linux) and explain how these elements have been brought together, even a mention of traditional UNIX would be useful, and why this was problematic in the past (i.e. compatability).
You need to cover licensing (and compare the FSF and OSS movements), and then compare these to proprietary systems, then go on to the actual Linux system. Try and avoid technical terms as much as possible and be sure to explain all things (i.e. if you mention file systems first clear up what a filesystem is).
Finally I'de recommend using examples of deployments from industry, especially famous ones like google.
I'de say the obvious focus is the server market, unless you want to give an overview of desktop usage - however this is not common in business so may not be as appropriate as focussing on the server end for students.
I'de recommend Open Sources -
here for info on open source and the fsf, also
Linux in a Nutshell and the
Linux Pocket Guide.