I just finished reading the classic book Diet for a Small Planet by Frances Moore Lappé. This was one of the first books, originally published in 1971, to make the link between diets heavy in meat and environmental, ecological, social justice and poverty issues. It's fascinating to see how it got started as a grassroots, unconventional movement and how today it is becoming a more mainstream, even fashionable (i.e. Skinny Bitch, as well as Mark Bittman and Michael Pollan's recent books) thing to cut back on consumption of animal foods.
Interestingly enough, Lappé points out that she does not necessarily "advocate what most people think of as vegetarianism". She pleads for a return to the diet on which our bodies evolved: mainly plant foods, with animal foods "playing a supplementary role". While she personally does not eat meat, she acknowledges, just like Bittman and Pollan, that a difference can be made to our health, the environment, animal welfare and social justice if we simply start by reducing the amount of animal products we consume.
One of Lappés original reasons for writing this book (which started out as a mimeographed pamphlet) was to show that it was possible and indeed easy to get enough protein for good health on a meatless diet. The book includes many recipes, all of them vegetarian, most include dairy and/or eggs, as they are all trying to provide plenty of protein.