Using a flash video with transparency, you can have a TV Presenter literally walk onto your website and give a short speech on your website to the web user. Or, you can just use a YouTube or vimeo embed code.
I specialise in green screen video production and have worked with various TV presenters that you might find on TV channels such as London Live, QVC, Ideal World and Sky 1.

Below are some video spokesperson videos filmed & edited by me:

Below is a explainer on my green screen video production services (Ultra Video Production is my trading as name):