The Plastic Pollution Coalition is a global network of businesses, organizations and individuals dedicated to improving the volume and impact of plastic pollution on the world. Their website has a great deal of useful background information on this problem.
The Surfrider Foundation also has some good information and resources on plastic pollution.
The National Resource Defense Council has a few ideas on reducing plastic waste.
Watch Ramin Bahrani’s excellent short film “Plastic Bag”, narrated by Werner Herzog.