On MSN's Money Central site under the Investing category there is a Portfolio Manager. This Portfolio Manager allows you to "purchase" stocks and "sell" stocks with no actual monetary exchange. This allows you to see what your investments would return if you were in-fact to invest. This is a great tool for teachers and beginning investors. As a beginning investor you can test your hand at picking stocks without the risk. For a teacher you can test your student's knowledge and understanding of financial ratios by making them analyze companies and choose what stocks to buy, and then monitor them.
You must create an account but it is free of charge.