In yet another..."you should check this out" entry, I'm fully endorsing Mark Bittman's blog...check it @ http://bitten.blogs.nytimes.com/ . I was lead there after reading excerpts from one of his newest books on diet, eating, and sustainable food production.
Some topics covered are things like outlining the benefits of eating a partially vegan diet (he uses something he calls the before 6pm rule)....and using the production method of food, rather than an organic label, to decide whether or not it is produced in a sustainable, healthy manor.
He also attempts to bring the restaurant mindset of "food cost" to the home kitchen by explaining recipes that cost virtually nothing to prepare. One example he uses is making beans and rice from scratch -- a meal that is nutritious, vegan, sustainable, easy to prepare, and costs less than $1 per person to serve.
He outlines another great reason to try to change 3 meals a week from meat-centric to vegan. Animal (as do people) produce greenhouse gasses. At last check, we raise 40 Billion - yes Billion -- animals for consumption in the US alone. If each of us dropped three meat items a week from our diet, we would be able to reduce the amount of animals raised and consumed to a level that would environmentally speaking, be equivalent to taking all of the SUVS driven in America off the road. Additionally, to raise this many animals to produce things like steaks and cheeses, etc, we use extremly efficient (yet not very nice for the animals) farming methods that are currently operating at 70% the capicity of the world's farmlands. With the world population rising, and our consumption levels increasing daily, we soon will hit a maximum level of production.
One last thing, Bittman has been eating a more plant based diet for the past 3 years, and with no increase in exercise, has lost 40 pounds. Think about it.