Leaving job Speech

I am leaving my current job on Thursday after just over 4 years with this company.

I have absolutely no idea what to say when I have the presentation, and hate talking in front of large groups - HELP!!!!!

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We have a number of articles that could help

Here is a link to two retirement speeches, which could possibly be customised into a leaving speech.
http://www.presentationmagazine.com/retirement-speech.htm