If you have not had a chance to explore podcasts I highly recommend you do it. There are many great sources that are free via a podcast. If you go to itunes and click on the itunes store there will be a button to push for podcasts. You then can begin searching for different podcasts. There are some neat podcasts done by the national parks, even Glacier National Park has one. One of my favorite podcasts is through National Geographic called Wild Chronicles. The episodes are short little videos that you can use for free to introduce a concept or to explore the world of science. There are many that are based on animals. My students love these short little video podcasts. Be sure that you watch the video first to make sure that is what you want to use. I think you will really like this option for your class.