NEW YORK (CNN/Money) - There's no doubt that 2003 has been a big year for stocks. Many companies have seen their shares soar to new heights, some have even doubled and tripled their worth.

The Dow Jones industrial average and the S&P 500 index are each up about 24 percent, as of Friday, with the Nasdaq up a whopping 48 percent.

Investors with positions in key technology and energy names have done well for themselves. Of the top five winning stocks in the S&P 500, two claim ties to the energy sector and the other three are members of the tech world.

Many of the companies posting the strongest gains were some of the hardest hit in 2002. In that year, seven of the top 10 losing stocks belonged to the energy sector. Four of the same 10 sinkers have reappeared in 2003's list of top gainers.

Here's a closer look at some of the biggest winners this year. (To find out which stocks were the biggest losers in 2003, click here.)

Avaya (AV: Research, Estimates), up 398.0 percent as of Friday. The communications systems and software developer has seen strong gains on the back of a resurgence in corporate spending. An increase in demand for computers and equipment, including Internet-based phone systems has provided a boost for the company.

Since Lucent spun off the company in 2000, Avaya has narrowed its losses, posting its first profitable quarter in July after a round of cost-cutting. In October, the company posted fiscal fourth-quarter earnings that soared past analysts' estimates and reversed a year-earlier loss. On Monday, J.P. Morgan raised its rating on the stock to "strong buy" from "market outperform," despite the stock's already hefty gains.

Other networking companies have also scored gains in 2003. Corning (GLW: down $0.08 to $10.32, Research, Estimates), which supplies high-speed fiber-optic networks, rose 210.0 percent, making it No. 6 on the top gainers' list. Avaya's former parent, Lucent (LU: down $0.01 to $2.85, Research, Estimates), came it at No. 20.

Williams Cos. (WMB: down $0.13 to $9.87, Research, Estimates), up 267.8 percent. The energy company, along with many of its counterparts, rebounded this year from the beating it took following the Enron scandal and a probe into its own trading practices.

Energy issues suffered in 2002 in the wake of allegations that executives took part in the manipulation of Enron's earnings to produce false and misleading financial results. Williams and others also faced allegations of misconduct during the California energy crisis in April 2000.

Tulsa, Okla.-based Williams, lost nearly 90 percent its value in 2002, ranking as the second biggest loser in the S&P.

In similar fashion, after tumbling 80 percent in 2002, AES (AES: up $0.20 to $9.49, Research, Estimates) has seen gains of 195.4 percent in 2003, which made it the No. 7 gainer this year.

Dynegy (DYN: down $0.04 to $4.31, Research, Estimates), up 262.7 percent. Like Williams Cos. and AES, the energy trader suffered in 2002 from the Enron scandal -- and an investigation of its own.

The Houston-based company lost nearly all of its value in 2002 after the Security and Exchange Commission announced a probe into its trading activities, which Dynegy eventually settled for $3 million. But the settlement didn't prevent the stock from sinking, or save the job of former chairman and CEO Charles Watson.

The company suspended energy trading on its Dynegydirect online systems, cut jobs, sold off units and lowered its financial outlook as a result of the investigation and was able to pull its shares higher, though they still remain in the $4 range, miles away from its high of 57 in 2001.

Dynegy fell more than 95 percent in 2002, making it that year's biggest loser.

PMC-Sierra (PMCS: up $0.13 to $20.26, Research, Estimates), up 250.9 percent. Like Avaya, PMC-Sierra also benefited from the beginnings of renewed economic growth and corporate spending in the second half of 2003.

The company broke even in the third quarter, despite Wall Street's expectations it would post a loss of a penny per share, and is forecast to report a profit of 2 cents a share in the fourth quarter, up from a 6-cent-a-share loss in the same period last year.

Chipmakers National Semiconductor (NMS: Research, Estimates), which claimed the No. 11 spot, and Advanced Micro Devices (AMD: down $0.19 to $15.09, Research, Estimates), landing at No. 18, also posted some of the strongest gains in 2003.

Novell (NOVL: down $0.03 to $10.51, Research, Estimates), up 215.9 percent. The software maker dusted itself off in 2003 after posting steep losses in 2002 and 2001.

Much of its share price gains came in November, after it announced it would buy German company SuSE Linux, which investors bet would help it compete with Microsoft (MSFT: up $0.01 to $27.47, Research, Estimates) and other Linux vendors like Red Hat (RHAT: down $0.02 to $18.96, Research, Estimates) -- as the company moves to sell customized versions of the software. Novell also owns a tech consulting company, which can help it sell and service its Linux products.

In November, the company posted a fiscal fourth-quarter profit of 5 cents a share, before charges, but sales fell 4 percent from the same period a year ago. Analysts expect Novell to post earnings of 22 cents a share in 2004.