Electronic Arts is one of the few pure software companies that continues to be important 25 years after its founding--and it wouldn't have existed at all if not for gaming pioneer Trip Hawkins, a Harvard and Stanford grad and Apple alumnus who in 1982 saw the future in consoles and computer-based games. Hawkins's foray into hardware--he left EA to launch the 3DO in 1991--met with considerably less success, but his first baby continues to thrive. Just ask John Madden.
44. Arianna Huffington
Political insider Arianna Huffington has had a major influence on technology, but one that has been felt only recently. She spent her early career inside the Washington, D.C., Beltway as a columnist, author, pundit, and TV show writer, far from the geek wiring of Silicon Valley. But in 2005 she launched a little online project called The Huffington Post, which rapidly grew into one of the Web's most powerful political voices. More than anything, the HuffPo has proven the power of the blog by attracting celebrity writers ranging from John Kerry to Jamie Lee Curtis, all eager to have their message heard through Huffington's medium.
45. Susan Kare
Another Macintosh 1.0 innovator, Susan Kare worked behind the scenes, but came up with essential innovations. Her earliest achievement was designing the typefaces--and  some of the, er, iconic icons--that shipped with the Macintosh. The "Happy Mac" remains one of computing's most visible expressions of things working well. Today Kare works as an independent designer: She designed the cards for Windows' ubiquitous Solitaire game and now designs Facebook's "Gifts" feature.
46. Sir Arthur C. Clarke
Sure, give Arthur C. Clarke credit for inspiring the minds of thousands of technology pioneers. But Clarke didn't just write seminal works of science fiction (including 2001: A Space Odyssey); he also conceived of geostationary communications satellites (satellites that orbit the earth at a speed proportional to the earth's rotation, so that the satellite always remains positioned above the same geographical point). Satellites with such orbits, sometimes termed the "Clarke satellite orbit," are essential to the telecommunications infrastructure, to GPS, and to numerous other technologies. Clarke died in March 2008 at age 90.
47. Herbie Hancock
When Herbie Hancock released his single, "Rockit" (from the album "Future Shock") in 1983, few listeners knew what to make of it. But everyone was struck by its unique sound--it was perhaps the first mainstream offering to use scratching. Though Hancock was by no means the first person to make heavy use of synthesizers, drum machines, and other computer-based musical equipment, few musicians relied so heavily on such gear and reached such a wide audience. "Rockit," with its innovative music video, is now considered a turning point in the electronic music-making scene, where Hancock is revered as an elder statesman.
48. William Gibson
The king of cyberpunk, William Gibson, has dreamed up all manner of high-minded techno wizardry, some of which has actually started to come true. His early stories introduced the term "cyberspace" and the visualization concepts behind it, which in turn prompted people to start thinking about networks in a way that transcended text and a command line. We may not be plugging chips directly into our brains yet, but Gibson's fiction-based prophecies have a strange way of panning out.
49. Gary Kildall
Called "The Man Who Could Have Been Bill Gates" by BusinessWeek, Gary Kildall was the guy Gates beat out in the bidding to supply IBM with the operating system for the original PC. According to legend, Kildall blew off the meeting with IBM to "go flying," though Kildall denied that rumor, posthumously, in his unpublished memoirs. Controversy aside, Kildall made significant contributions to the tech business--especially as the head of Digital Research, which created the seminal pre-DOS operating system CP/M, and (later) as a host of the classic Public TV program, Computer Chronicles. Kildall died in 1994.
50. Udi Manber
If there is a search engine anywhere that doesn't have the thumbprint of Udi Manber on it, we don't know about it. From Yahoo to Amazon's A9 to Google, Manber has been one of the search business's greatest contributors. But Manber's work goes back even farther than that, to AltaVista. He was a key member of the design team on what many feel was the best engine running until Google came along.
Christopher Null writes regularly for PC World and blogs about technology daily at tech.yahoo.com.