Choose a company and compute its stock beta yourself.

A common estimation procedure is to use 60 months of return data and to use the S&P 500 Index as the market portfolio.

You can obtain price data for a company and for the S&P 500 Index for free from Web sites like Yahoo! Finance. Using monthly prices, you can compute the monthly returns, as (Pn Pn-1) / Pn-1.

Once you have your previous 60 monthly returns for both your stock and the market index, use the SLOPE function on excel to find beta.