Math Pickle is a nice site for locating videos and exercises appropriate for teaching a variety of mathematics concepts at a variety of grade levels. When you visit Math Pickle you can browse for videos by grade level. Once you’ve selected a grade level you can then refine your browsing to a particular concept. Each concept has a demonstration video and links to Keynote and Powerpoint files for teachers. Each concept also has links to PDF worksheets that you can download and print.