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It's been a rocky year for the stock market. Shares hit troubles early in the year, experienced a sudden one-day tumble in the spring that's been blamed on newfangled electronic trading and have managed to rebound lately.

With money market rates near zero and yields on many bonds as low as they've been in recent memory, some investors are struggling to find sources of steady income. Some have piled into shares with respectable dividends, figuring a 4% or so dividend yield is about as much as they can expect.

The Dow Jones Industrial Average ($INDU) is now up 6.8% for the year; the Standard & Poor's 500 Index ($INX) is up 6.1%. Meanwhile, the dollar has continued to fall against other major currencies, and gold is going for $1,325 an ounce.

But for a select group of superstar stocks, 2010 has been nirvana. Shares of Cummins (CMI, news), Akamai Technologies (AKAM, news), Zions Bancorp (ZION, news), Lexmark International (LXK, news), Family Dollar Stores (FDO, news)and Priceline.com (PCLN, news) have soared this year, trouncing the market.

Volatile shares that do poorly during big market drops often have more upside potential when markets rebound. Indeed, many of these same winners tumbled sharply during the bear market. Between March 7, 2008, and March 9, 2009, as the S & P 500 fell 46%, Cummins, Akamai, Zions and Lexmark each dropped about 65%.

"Cyclical stocks whose prospects are deeply tied to the economy, particularly those that were most sharply battered leading to the March 9, 2009, market bottom, are the same stocks whose fortunes have turned the sharpest," says Alan Zafran, a co-founder of Luminous Capital, a West Coast investment advisory company.

That's not enough of an explanation for the gains of this year's winners, however, because some stocks, such as Family Dollar, had managed to rise during that brutal period.

Here's an analysis of this year's superstocks with the goal of understanding why they've done so well, whether their rallies will continue and how investors can learn to find other beauties for their portfolios.

Cummins: Up 104% this year

Back story and lesson: Industrial and manufacturing companies have rebounded this year. These businesses were hurt the most in the downturn -- and benefited the most as the economy stabilized. A weaker dollar has helped.

Cummins, which designs, manufactures, distributes and services diesel and natural-gas engines, has gained from the push toward cleaner engines.

Future: Cleve Rueckert of investment firm Birinyi Associates advises waiting until there's some bad news on the stock before selling. More than ever, he says, stocks with momentum should continue to do well.

Oct. 22 closing price: $93.63.

Akamai: Up 88% this year

Back story and lesson: Akamai, which provides services for companies doing business on the Internet, has posted record revenue. It has benefited from the streaming Internet world and growth of services such as movie provider Netflix (NFLX, news).

Future: Akamai is now expensive, trading at 41 times next year's expected earnings. Switching to cheaper and larger tech companies could pay off. Some investors, such as Lee Ainsle of hedge fund Maverick Capital, note that larger tech stocks are inexpensive and safer bets over the next two years. His company is a big holder of tech shares, including Hewlett-Packard (HPQ, news).

Oct. 22 closing price: $47.61.