Ethics of Eating Meat
I've always said that I think you could base a plausible (if not necessarily correct) argument for vegetarianism simply on our duties to fellow human beings, thus avoiding tricky questions about animal rights or suffering. In a world marked by over-crowding, food shortages, and global warming, it may be that the world's population could be better-supported if we were all (at least nearly) vegetarian.
It seems that Sir Paul McCartney is on board with the idea, suggesting that people give up meat on Mondays. (Though the cynic in me wonders whether he'd profit from increased sales of his ex-wife's vegetarian alternatives, I applaud the sentiment.)
Of course, though, another alternative would be if we could artificially grow our own substitutes, which might remove many of the ethical objections (though, as my girlfriend points out, artificial meat grown by cloning animal cells still wouldn't be vegan).