This was an interesting article on CNN. Turns out that, except for petroleum manufacturing, Hollywood caused more pollution than any other sector in and around Los Angeles. Some other cool information was that some films try to offset their damage. The second two "Matrix" movies recycled 97.5% of the set materials, while "The Day After Tomorrow" spent $200,000 planting trees.
Now, if some high-paid actors would just give up 10% of their normal fee, rather than simply offering their face as a poster child for a campaign to convince everyone else to donate.
http://www.cnn.com/2006/US/11/14/hollywood.pollution.ap/index.html