This site has some flash animations. My favorite are the two Robocow animations in which a robotic cow encounters various forms of point source and non-point source pollution problems and demonstrates how to correct them. The kids love these ones and they make for great conversations.
This website has great animations (fun too!) that cover a wide range of topics. You can do a free 5 day trial and would then need to subscribe to it. I think it is worth it!
This site deals with acid rain, explaining what it is, how it is causes, why it is harmful, what is being done, etc. It also has games/activities and a video clip.
This is a fun and interactive website that takes students through different parts of the water cycle and how it is affected by humans. It is in the form of a water festival and they click on the tents to view different topics pertaining to the earth's water.