The S&P 500 is up 2.9% for the year, and its cyclically adjusted price-to-earnings ratio is still high at 31 times. Not all stocks move in unison, though, and several companies are now trading their lowest levels over the past year. For investors looking to take advantage of the short-term thinking of the market, the occasional great company can be found on the 52-week low list. Today, three that stick out as great companies to own for the long-term…