This clip from the HowStuffWorks show on the Discovery Channel discusses the use of corn to make plastic.
Plastic made from corn is biodegradable, carbon-neutral and in some cases edible. The link was sent to me by Tina VanHoogstraat the ASI contact at QuickPoint, one of the promotional items manufacturers using corn plastics and other new materials to make drinkware and other items for the promotional items market.
The clip is a basic overview. Don’t expect a hard hitting expose, the clip is more about hows than whys. It does have input from some people you might recognize like author Michael Pollan – FYI I am reading In Defense of Food currently and really enjoying it.
If you are interested in corn plastic promotional items to promote your own business contact your local promotional items vendor or email info@proformagreen.com for information and pricing.
Adventures in Green Marketing 
That is such a cool video. I was wondering how they were making plastic out of corn. I wonder if they can make it out of other things that contain starch?