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http://www.bogonomicon.org/bblog/ocaml.sxi (OpenOffice Presenter format)
This talk by Brian Hurt is designed for Unix/Linux User Groups and other technical audiences. It's quite lengthy and in-depth, but overall excellent. It is licensed under a Creative Commons license.
Richard W.M. Jones also gave a talk to his local LUG. However it's not currently in a state to be put online. This talk was short (15 minutes) and just a short technical overview of features.