Stocks mostly fell today as Janet Yellen said she and other Federal Reserve bankers believed that some stock valuations in certain sectors had been "stretched." In a report accompanying her congressional testimony, Yellen called out social media and biotech firms in particular, which are some of the most volatile stocks in the market. The Dow Jones Industrial Average (DJINDICES:^DJI) battled back to finish essentially even, gaining 5 points or 0.03%, while the S&P 500 lost 0.2% and the Nasdaq dropped 0.5% as it's home to many of the small-cap stocks that Yellen was referring to.

Elsewhere, June retail sales were much lower than expected, coming in at 0.2%, the slowest pace since January, versus estimates of 0.7% growth. The reading seemed to confirm early reports from retailers that the second quarter was slow despite strong job growth and other positive economic data, as well as an expected bounceback from negative growth in the first quarter due severe weather. Growth in June was down from 0.5% in May, which was revised up from 0.3%. Also, excluding the auto industry, retail sales would have grown 0.4% last month. In the day's other reports, the Empire State manufacturing survey soared to 25.6 this month from 19.3 in June, and easily beat estimates at 13.2. The reading hit a four-year high and indicates a robust expansion in manufacturing activity in the Northeast.

Apple (NASDAQ:AAPL) shares were moving higher after hours today, gaining 1.7% on a deal with IBM to work together to and make more apps for business customers and sell phones and tablets to that segment. The agreement seems to combine Apple's know-how with IBM's customer base as Apple has traditionally struggled to win over the corporate and government market, which had been a strength of BlackBerry's. Shares of BlackBerry notably fell 3.7% on the news. Apple is planning on releasing the apps this fall, which will include IBM technology designed for business clients that need heavy data-processing capabilities. The move seems like a win for both companies and is a reflection of Apple CEO Tim Cook's strategy of looking outward for help rather than the independent streak that seemed to represent Apple under Steve Jobs.

Finally, tobacco stocks sold off today as Reynolds American acquired Lorillard (UNKNOWN:LO.DL) went for a lower price than expected, purchasing the No. 3 U.S. tobacco company for $68.88 a share when many analysts expected the price tag to be north of $70. Lorillard shares finished down 10% and Reynolds American dropped 8% as Lorillard's blu e-cigarette brand, the industry leader, will not be part of the deal -- the company plans to spin it off. Blu's separation seems to owe to antitrust concerns, and also because Reynolds believes its Vuse e-cig has better technology. Other tobacco stocks fell as the underwhelming sale price seems to be bad news for the low-growth industry as a whole.