I found this the other day on youtube - it's from 2007 so apologies if it has been posted and discussed here already (I searched and found nothing). I didn't used to care or worry very much about population growth, nonrenewable resources and so on but recently films like Fast Food Nation, The Corporation and now this video have started to sway me.
It's a lecture by Dr Albert A Bartlett, a physics professor. It lasts about an hour but doesn't seem that long as it's very compelling, and delivered in simple language that anyone can understand it. I haven't ever heard the planet's problems articulated as directly, urgently or persuasively as in this video; I'm posting it here because I think it's pretty important that as many people as possible watch it.