Standard and Poor 500: http://www.google.com/finance?q=SPY http://en.wikipedia.org/wiki/S&P_500

Russell 3000 Index: http://www.google.com/finance?q=IWV http://en.wikipedia.org/wiki/Russell_Indexes

These are highly correlated over the short run, but technically different investments. So, you can get cute with the taxman by writing off a loss on one and buying into the other every down year.