Standard & Poor’s 500, 400, 600
Some experts prefer the S&P 500 index, which includes a representative sample of 500 leading companies in the leading industries in the U.S. Although they focus on "large-cap" (largest market capitalized firms), they represent more than 80% of the stock market. The S&P, like Dow Jones, has many other indexes. For example the S&P 400 tracks 400 mid-cap stocks and the S&P 600 tracks 600 small-cap stocks. Visit their website for information and the other indices they have: http://www2.standardandpoors.com
