investing.money.msn.com/investments/market-summary/
finance.yahoo.com
These extensive sites include historical price information for estimating average returns, standard deviations, and covariance of returns between securities.

www.financialengines.com
This site provides risk measures for individual stocks and good portfolio analytics.

www.moneychimp.com/articles/risk/risksimulator.htm
This site provides a simulator for portfolios of cash, stocks, and bonds. It also has a link to a portfolio “optimizer.”

www.duke.edu/~charvey/frontier/
An interactive efficient frontier at this site allows the user to see how the frontier changes as various asset classes are added.

www.smartmoney.com/marketmap/
This site contains an interactive map that shows various market sectors and the firms within the sectors.

www.investopedia.com/university/optionvolatility/#axzz27cDFSEhx
This site offers a tutorial on stock market volatility.