Being a billionaire may not be quite the exclusive club it once was, but let's face it: A billion's a tidy sum, no matter how you slice it. As the list of billionaires continues to grow, there are several names, and the stories to go along with them, that fly under the radar. Sure, we all know names like Gates, Zuckerberg, Buffett, and a host of others.

But as new technology sectors including mobile, cloud, big data, and a host of others, continue to grow, the future list of billionaires is likely going to be even longer. So, who are these folks making all that money? Here are a few, and the stories behind their successful run to billions.

From vegetable oil to technology
Following the untimely death of his father in 1966, Azim Premji dropped his electrical engineering studies at Stanford and returned home to India to take over the family business, Western India Products, or WIP. At the time, WIP was a successful producer of hydrogenated vegetable oils and laundry soap, and Premji's family business was worth an estimated $2 million. A tidy sum, to be sure, especially in the late 1960's. Though not quite billionaire material.

But a return to his engineering roots meant big changes at WIP. Premji reinvented the company in 1980 as an IT service provider, and Wipro Limited (WIT 0.90%) was born. Wipro went public 15 years later, and remains one of the largest software and enterprise technology concerns in India. As Wipro grew, so too did Premji's wealth. With an estimated net worth of $16 billion, Premji still runs Wipro today as acting chairman of the board, CEO, and managing director, and is the second wealthiest person in India.

Apple? Who needs Apple?
Robert Pera didn't have to move far when he accepted his first job after earning his master's degree in electrical engineering from UC San Diego. Pera actually grew up not far from the tech capital of the world, and returned after joining iEverything maker Apple fresh out of school. For many tech geeks, working at Apple would be a dream job -- the culmination of all the studying. But as Pera described it, "Apple is a great company, but I realized I wanted to have more success faster."

Turns out, Pera's youthful exuberance was warranted. Using a combination of his savings and credit cards, Pera scrounged up about $30,000 and started Ubiquiti Networks (UI 1.94%), a provider of wireless broadband and wireless networking solutions, among other products and services. Today, Ubiquiti Networks is valued at about $3 billion, and Pera's net worth is estimated at $2.1 billion. Pera is also head of a partnership group to buy the NBA's Memphis Grizzlies: not bad for a 36-year old.

From riches to rags, and back again
Long-time partners David Sun and John Tu have not only come a long way to attain their success, and the estimated $4.5 billion in wealth each is currently worth, they've both suffered through the pain of losing it all, and starting again. That Sun and Tu made it back from the financial abyss is a marvel in and of itself, the fact it happened to these two proves that nice guys don't finish last.

After traveling across the globe from their respective birthplaces -- Sun was born in Taiwan and Tu in China -- the two engineers met in 1982 and promptly started a computer memory chips company called Camintonn. Like many good tech success stories, Camintonn began out of Tu's garage. In four short years, Camintonn was generating $9 million in annual revenues, and the two partners decided to cash in; selling their company for $6 million. Sun and Tu invested the sales proceeds in the stock market, losing almost everything the following year in 1987's crash.

Down but not out, Sun and Tu designed the then ground-breaking Single In-Line Memory Module, or SIMM, and with that, along with $4,000, started Kingston Technologies. In 1996, the two billionaires pulled off a wonderful coup: selling 80% of Kingston Technologies to Japan's Softbank for $1.5 billion. Not surprisingly, Sun and Tu then used $100 million of the proceeds to surprise their employees with a huge bonus. As for the 80% of Kingston sold to Softbank? The two billionaires bought it back in three years for $450 million.