As the U.S. markets have sharply rallied over the past few months, many of the consumer staples stocks have watched the action from the sidelines. Since the end of August, the S&P 500 has tacked on nearly 25%, while high-quality giants like PepsiCo (NYSE: PEP) and Procter & Gamble (NYSE: PG) have gained 4% and 10%, respectively.

Will the new year bring some new pep for consumer staples stocks? A lot will depend on a few broad themes at work in the sector.

What to watch
There are three primary themes that I'll have my eye on in the coming year when it comes to the consumer staples sector: the economy, private labels, and emerging markets.

The economy. Yawn, right? Yes, it's talked about to death, but it's not something we can skip over. The consequences of the state of the economy aren't terribly straightforward either. Obviously it's tougher on pretty much all consumer staples companies when consumers get pinched, but some companies -- like lower-end retailers such as Wal-Mart (NYSE: WMT) -- can benefit from consumers' search for deals. Others, like Altria (NYSE: MO) and Molson Coors, sell products with relatively inelastic demand and don't fret as much about recessions. Heck, those companies may actually do better during recessions as consumers look to ease their stress.

If the economy continues to be sluggish the picture isn't quite as bright for companies like P&G and Colgate-Palmolive (NYSE: CL) as consumers may choose dollar value over brand value. But even for those companies, there could be opportunity if they're working their way into the lower-priced segments of their markets. This has been part of the strategy for P&G as it seeks to cover a broader price range in its product categories. Winning customers with lower-cost products during tough times could mean more customers grabbing higher-priced products when times are brighter.

The private-label issue goes hand in hand with the economy to some extent but is also a theme unto itself. Major branded-goods makers have been battling against the private label offerings from retailers like Wal-Mart, Target, and Kroger (NYSE: KR), and the recession was a boon for private-label offerings as consumers traded down. The question now will be whether, as the economy recovers, branded consumer staples will win back market share and stymie the inroads that private labels have made.

Finally, there are the emerging markets -- also known as the land of milk and honey for consumer-staples companies. I think this excerpt from P&G's December analyst meeting tells much of the story:

In China, over the next decade, 270 million consumers will be added to the "middle-income and affluent" ranks ... roughly the same number as there are in the U.S. today. ... 41% of "middle-income and affluent consumers" said they plan to trade-up to more expensive products --"especially in packaged goods and clothing."

Is there any wonder that the emerging markets are a big deal for these companies?

3 picks
While I see the above factors broadly moving the sector, I'm generally more of a bottom-up investor who looks for individual companies that are well run, have opportunities ahead of them, and whose stocks are a good value.

Here are three I think are well worth having on your watchlist for 2011.

The retailing giant hasn't been exceedingly impressive lately, but I still see the company as extremely well positioned. If the economy continues to struggle, more cash-strapped consumers will find themselves shopping for deals at Wal-Mart, while if the economy improves, its core customer base will have more money to spend. Meanwhile, Wal-Mart's global growth opportunity is so compelling that Motley Fool Global Gains advisor Tim Hanson named it his top international pick for 2011. Wal-Mart pays a decent 2.2% dividend, and it's doubled its payout over the past five years. Meanwhile, the stock trades at a mere 12.6 times its estimated forward earnings. (Add Wal-Mart to your watchlist.)

Clorox (NYSE: CLX)
This generally isn't the first name that comes to mind when thinking about the major consumer-staples stocks, but that's part of the reason I like Clorox. Though the name conjures up a boring image of bleach products, Clorox also houses brands such as Glad, Brita, Burt's Bees, and Hidden Valley. While the forward P/E of 15.5 may not seem terribly cheap, the company produces gobs of free cash flow, which I believe makes it a more valuable stock than it seems at first glance. And the market's recent pessimism when it comes to Clorox has only piqued my interest further. (Add Clorox to your watchlist.)

There are a handful of companies that I could have put in this final slot and many are cheaper than PepsiCo. However, with a forward P/E of 15, I still think PepsiCo offers decent value -- particularly when compared with its main archrival Coca-Cola, which trades at a multiple of 17. But PepsiCo also offers a good deal of diversity: Along with an array of beverages, the company also boasts the whole Frito-Lay and Quaker Brands catalogs. Strategy-wise, I think the company may really be on to something with its push on the "nutrition" angle. More anecdotally, I also have to admit that I was impressed after recently trying the Gatorade G Series for the first time -- most of the time I might snicker at the word "innovation" being used with beverages, but I think the shoe fits here. (Add PepsiCo to your watchlist.)

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Coca-Cola, Molson Coors and Wal-Mart are Motley Fool Inside Value recommendations. Wal-Mart is a Motley Fool Global Gains pick. Coca-Cola, Clorox, PepsiCo, and Procter & Gamble are Motley Fool Income Investor picks. The Fool owns shares of and has written covered calls on Procter & Gamble. Motley Fool Options has recommended a diagonal call position on PepsiCo. The Fool owns shares of Altria, Molson Coors, Coca-Cola and Wal-Mart. 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.

Fool contributor Matt Koppenheffer owns shares of Wal-Mart, but does not own shares of any of the other companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.