For our fifth annual roundup, BusinessWeek readers nominated a record number of young entrepreneurs. Meet the 25 most impressive

Welcome to our fifth annual roundup of the country's most promising young entrepreneurs. Before we get started examining the new batch, consider this question: Who is more likely to start a business: A college student or a worker with a few decades of experience? Yep, you guessed it: the experienced worker.

It turns out it's boomers, not twentysomethings, who start the most businesses in the U.S. Over the past decade or so, the highest rate of entrepreneurial activity belongs to the 55-64 age group. The 20-34 age bracket, by contrast, had the lowest rate. That's according to a recent report by Dane Stangler, a senior analyst with the Kauffman Foundation, based on data collected from 1996 to 2007. It echoes research by entrepreneur-turned-academic Vivek Wadhwa, who found that twice as many tech entrepreneurs create ventures in their 50s as do those in their early 20s.

So not only are these entrepreneurs navigating the toughest economy many of us have ever lived through, they're also vastly outnumbered by older, more experienced competitors, who usually have more contacts and capital. That's even more reason to continue to give young entrepreneurs the encouragement, respect, and awe that they've received since becoming cultural icons during the dot-com boom.

Stangler says he's not suggesting young people aren't entrepreneurial or won't be. "The cachet of large, established companies has taken a hit. Job tenure has been falling for a long time. Employment is not going to recover in the very near future. People across all age groups are going to take the future into their own hands."

Dorm Room Beginnings

Brian Ruby, 25, is just one entrepreneur who is following through on Stangler's prediction. He founded molecular imaging equipment maker Carbon Nanoprobes in 2003 in his Columbia University dorm room and has since raised about $4 million from institutional and private investors. After six years doing research, Carbon Nanoprobes is now transitioning to equipment sales, and Ruby expects about $1 million in revenue in 2010. The nine-person company based in Pike Malvern, Pa., sells its equipment to universities, semiconductor firms, and material sciences companies.

Husband-and-wife team Eric Koger, 25, and Susan Koger, 24, launched indie clothing e-tailer ModCloth in 2002, near the end of their freshman year at Carnegie Mellon University. They've managed to raise a little over $3 million from angels such as StubHub co-founder Jeff Fluhr and venture capital firms First Round Capital and Maples Investments. Eric says the 104-employee, Pittsburgh-based company is profitable, with around $1 million in monthly sales, and forecasts more than $15 million total in 2009.

Logan Green, 25, and John Zimmer, 25, started Zimride in 2007 to allow carpoolers to connect online. Its 35 clients are mostly colleges but include corporate customers such as Cigna (CI) and Wal-Mart (WMT). Universities pay about $10,000 per year to use the platform, although pricing varies. Zimmer says the Palo Alto (Calif.) firm, with six employees, expects revenue of $400,000 this year and is now profitable.

Record Numbers

These are just a few of our finalists defying the odds. To assemble the group, as in previous years, we asked BusinessWeek readers to nominate candidates aged 25 and under who were running their own companies that showed potential for growth. Given the severity of the recession, we were pleased to receive a record number of nominations this year -- more than 600. After the call for nominations ended in mid-August, our staff sifted through the nominees looking for the most impressive.

Not surprisingly, the majority were Web-based businesses, where barriers to entry continue to fall. There were a smattering of more traditional companies, including an aircraft seller, a specialty mushroom grower, and a machinery lubricant vendor. Compared with last year, more women were nominated, more businesses were profitable, and more had secured equity capital.

You can flip through this slide show for profiles of each of the 25 finalists, then vote for the business you feel holds the most promise. We'll announce the top vote-getters on Nov. 9. Then check out our slide show on where last year's finalists are now. For more elements of the special report, including a feature on selling to universities and a video interview with a standout alum, visit the related items box at upper right side of this overview.

U.S. Entrepreneurs Ages 25 and Under

This summer, BusinessWeek set out on its fifth annual search to find the country's most promising young entrepreneurs. As in previous years, we asked readers to nominate candidates ages 25 and under running their own companies. After the call for nominations ended in August, our staff whittled the batch down to 25 impressive businesses. To read profiles of the finalists and vote for the business you feel holds the most promise, click on. We'll announce the top vote-getters on Nov. 9.

1. Ascension Aircraft

What It Does: Aircraft sales and leasing
Founder: Jamail Larkins, 25
Web Site: www.ascensionaircraft.com
Based: Augusta, Ga.

Jamail Larkins has been hooked on flying ever since he took his first flying lesson at age 12. The Augusta (Ga.) native completed his first solo flight at 14, performed in an aerobatic air show four years later, and earned a bachelor's degree in aviation business administration from Embry-Riddle Aeronautical University. But instead of following a traditional career path and going to work for Boeing (BA) or Lockheed Martin (LMT), Larkins decided to channel his passion into his own business. It came naturally. At 15, he had started Larkins Enterprises, selling flight training books and videos to local pilots, to pay for his flying lessons. "I promise you we started off selling a lot less than we do today," he says. Though he continues to run Larkins to do marketing and consulting for clients that include his alma mater, the National Business Aviation Assn., and Michelin Aircraft Tires, he says 90% of his revenue comes from his aircraft sales and leasing company, Ascension Aircraft, which he started in 2006. Larkins says four-employee Ascension is profitable and had a little over $7 million in revenue in 2008, despite the downturn. He expects revenue to increase slightly this year. He continues to fly for fun every chance he gets and is planning to get back into aerobatics in 2010.

2. Box.net

What It Does: Online collaboration tool
Founders: Aaron Levie, 24, and Dylan Smith, 24
Web Site: box.net
Based: Palo Alto, Calif.

Aaron Levie and Dylan Smith started Box.net in 2005, when they were both college sophomores, as a tool to collaborate on projects with fellow students. The pair -- childhood friends from Seattle -- soon saw business potential in an online platform to let companies share information securely. Nine months after launching, they both left school (they were at University of Southern California and Duke, respectively) and moved to the Bay Area to work on the company full time, with an initial $350,000 investment from Mark Cuban. (His stake has since been bought out.) The service, targeted toward companies with fewer than 100 employees, has 3 million users representing 50,000 businesses. Individuals can try a limited version for free, but businesses pay $15 per user per month for the premium version. The company, now based in Palo Alto, has 50 employees and has raised $14.5 million in venture capital from Draper Fisher Jurvetson and U.S. Venture Partners. The firm is not yet profitable, though Levie says revenue is in the "mid-to-high single millions," and he expects it to turn a profit soon.

3. Click To Client

What It Does: Online marketing agency
Founder: Shama Kabani, 24
Web Site: www.clicktoclient.com
Based: Dallas

While completing her master's degree in organizational communication at the University of Texas at Austin, Shama Kabani wrote her thesis on why people use Twitter and other social networking sites. She became convinced businesses could use the tools to market their products and services. But when Kabani made that pitch as she applied for jobs at big management consulting firms such as McKinsey and Bain & Co. in 2006, she was rejected. "At that point, nobody really cared for social media knowhow. They were just thinking, 'This is a fad. Our clients don't really need it.' " Undeterred, Kabani, whose parents are both entrepreneurs, founded her own full-service online marketing firm in March 2008, to build Web sites, handle SEO, and create and manage social media campaigns. The six-employee business now takes on about 25 one-off projects a month and also acts as an online marketing department for six regular clients on a retainer basis. Fees range from a few hundred dollars for a newsletter design to $2,500 for a Web site project; monthly retainer fees start around $2,500. Kabani says Click To Client had about $120,000 in revenue in 2008, expects $280,000 for 2009, and is shooting for $1 million in 2010. Her first book, The Zen of Social Media Marketing, is due out in April.

4. Emergent

What It Does: Renewable energy consulting
Founders: Jesse Gossett, 23 (left); Jayson Uppal, 23 (center); and Chris Jacobs, 21 (right)
Web Site: www.emergentgroup.com
Based: Boston

Two years ago, three Tufts University students and one Babson College student attended the Energy Security Initiative at Tufts (now the Tufts Energy Forum), a group whose mission is "to spread and enhance the discussion surrounding all aspects of the transforming, global energy industry." It was there that Jesse Gossett, Jared Rodriguez, Jayson Uppal, and Chris Jacobs decided there was a need in the consulting sphere to help guide municipalities and private businesses toward using renewable energies and setting up sustainability practices. The quartet spent their final year in college researching and readying a business to do just that. Before they graduated, they landed their first consulting contract. Emergent now has about 30 clients, mostly municipalities, including the towns of Yates, Shelby, and Orleans County in western New York. The firm had $108,000 in revenue last year, and estimates it will reach $250,000 in 2009 and become profitable by 2011.

5. I Bec Creative

What It Does: Web development and graphic design
Founder: Becky Stockbridge, 25
Web Site: www.ibeccreative.com
Based: Portland, Me.

While a senior at the University of Southern Maine, Becky Stockbridge wrote a business plan to start a Web and graphic design business for medical professionals, a group she found was in need of logos, brochures, and informative Web sites -- and who also had the money to pay for them. She got started in 2006 with a $4,200 grant from the Libra Future Funds, a Maine-based group that helps entrepreneurs under 25. The Maine Center for Enterprise Development awarded her free office space for one year. However, Stockbridge says she found it difficult to get through to the decision-makers in medical practices. While she struggled to make contact, Stockbridge began designing Web sites and logos for other small businesses. By 2007, she had more business clients than doctor clients and shifted her focus. Last year the five-person company had about $225,000 in revenue and Stockbridge expects $350,000 in 2009.