As recently as last year I heard the point made that corn based ethanol was not an energy efficient alternative fuel, that in the end it was a net negative; in other words, it took more total energy to produce the ethanol than was saved by using it. Now, a new study claims that ethanol from corn can yield more energy than is used in making it.
For more on ethanol and the role it might play in our future, see this USA Today article.
Also, I found it interesting that many of the reports on Brazil's successful use of sugar based ethanol have ommited the fact that croplands used to grow the ethanol producing plants were created out of swaths of Amazon jungle (aka rain forest). I did find reference to it in this article, "Study Boosts Ethanol as Fuel".