Great video by PBS, can be found on youtube. Is lengthy but is good if you add some activities in between viewing. I modified a worksheet (originally created by Daniel H Smith, Moorestown High School, Moorestown, NJ), and created a key that goes along with the video. Other resources can be found here http://www.pbs.org/wgbh/nova/teachers/ideas/28gm_harvest.html
Visit http://www.pbs.org/wgbh/harvest/ for additional resources and online activities. The video in regards to the transgenic salmon is a great video to show as well.