"A simple rule dictates my buying: Be fearful when others are greedy, and be greedy when others are fearful."
-- Warren E. Buffett 

The U.S. stock market used to set the tone for equity markets worldwide; right now, all eyes are on China. The near-9% loss Chinese stocks suffered on Monday has traders rattled, as the S&P 500 (SNPINDEX:^GSPC) fell as much as 5.3% in the first five minutes of trading. Stocks have recovered well, however, with the Dow Jones Industrial Average (DJINDICES:^DJI) and the broader S&P 500 down 0.83% and 1.07%, respectively, at 1:20 p. m. EDT. The Nasdaq Composite was down 0.49%.   

For traders, the spike in stock price volatility over the past week has real consequences -- the sort you can feel in your gut. However, patient, value-driven investors are starting to lick their chops. Where it had become very difficult to find investment value in a market that had become increasingly expensive, stock price declines mean the opportunities have multiplied.

It's a challenge to keep trepidation in check when the prevailing sentiment is confusion and even panic, but those who are capable of doing so can make some splendid investments today and, very likely, over the next few days, that ought to pay off handsomely in the years to come. 

(Of course, you need cash on hand on top of the proper emotional disposition in order to seize these opportunities.) 

Last week, I did a three-part series on the relative attractiveness of emerging markets, but I think it's now appropriate to turn my attention back to the U.S. Without further ado, here are two world-class businesses that are currently on offer at prices that are finally reasonable -- and, in the case of Apple, legitimately cheap. 

Apple
With China now Apple's second-largest market, the upheaval in the Chinese stock market and concerns about slowing growth have compounded a big sell-off in the shares of iPhone maker. Based on Friday's closing price of $105.76, the stock has fallen nearly 20% since July 20. 

There's no doubt that the current turmoil in China could hurt demand for Apple products in the near term, but ask yourself: Do you expect Apple's franchise in China to grow or shrink over the next 10 years? 

That's the sort of time frame that Tim Cook has in mind as he makes decisions regarding expansion in China. There is no reason for investors who own Apple shares or who are considering buying them to adopt a time frame that is any shorter! 

The shares are now changing hands at roughly 11 times next year's earnings estimate – and this doesn't account for a cash pile that represents approximately one-third of the company's market value! This is as close to a slam-dunk as you are likely to be offered in the stock market. 

Mead Johnson Nutrition
From the most visible large-cap stock in the world to one that is overlooked: This is a stock I have mentioned before that appears to be flying far under Wall Street's radar. That's a shame because Mead Johnson Nutrition is "Berkshire-worthy" -- i.e., it's the kind of high-quality consumer franchise that Warren Buffett would be delighted to bring into the Berkshire Hathaway family of companies in an outright acquisition. 

Spun out of Bristol-Myers Squibb in early 2009, Mead Johnson is a world leader in manufacturing infant formula and child nutrition. Do you think a parent might be loyal to a brand that has established a sterling reputation for quality when it comes to choosing what they feed their baby? That brand and reputation are at the root of the company's durable competitive advantage. 

At over 19 times next year's earnings estimate, the shares aren't a screaming bargain, but don't get hung up on that. In my estimation, they are fairly valued (at worst) and that ought to be more than enough for shareholders to earn a very satisfying return over the next five to 10 years.

Alex Dumortier, CFA has no position in any stocks mentioned. The Motley Fool owns and recommends Apple and Berkshire Hathaway. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.