[Updated Oct. 7, 2011]

Tim Berners-Lee, director of the World Wide Web Consortium, and inventor of the Web (from his blog, with permission)
A big thing Steve Jobs did for the world was to insist that computers could be usable rather than totally infuriating!

The NeXT was brilliant. The NeXT had (arguably too) many things introduced at once—removable optical storage, Objective C, DSP for sound and movies, Mach kernel, unix for a PC, display Postscript, InterfaceBuilder and so on. Yes, they never got the price down and the optical disks proved unreliable. But Steve and NeXTStep ended up saving Apple, and there must be a lesson that it is worth hanging on to cool things: you never know when they will in fact become mainstream.

Michael Hawley, MIT and former colleague at NeXT:
Honestly, Steve was like the older brother I never had. We had wonderful adventures working and making things together—but what we shared as pals was worth so much more. The world will be going crazy with outpourings, which is wonderful but somehow surreal and out of proportion with the day-to-day way we worked and walked together, just a couple of guys.

One of my favorite memories was his habit of just asking if I wanted to take a walk. Sometimes it would be a walk around the parking lot (not real scenic), or down the street from his house to the little park and back—just to walk, and talk about stuff. [Wednesday] evening I was in Washington at dinner, an early dinner with a couple of friends. It was a very brief call—John Markoff from The New York Times. I answered and said, "Steve?" and he said, "Yes. Sorry." I hung up—and stepped outside the restaurant, and took a little walk.

John Hennessy, Stanford University president:
Steve Jobs was an extraordinary man, and I am deeply saddened to learn of his death. A pioneer in the computer industry, his creativity and vision are legend. But he was also a great communicator, who was able to cultivate innovation in others. When he spoke at Stanford's 2005 Commencement, he told our students that the key to doing great work is to love what you do. Steve Jobs loved what he did, and he inspired us all to think differently. He will be profoundly missed.

Jonathan Zittrain, professor of Internet law at Harvard Law School:
Arthur C. Clarke famously observed that any sufficiently advanced technology is indistinguishable from magic. Steve Jobs grasped the value of not keeping technology's wiring exposed: when an early Mac went awry it showed an unhappy face or an old fashioned cannonball bomb with a lit fuse, instead of a debug screen. And with nearly every new product—another rabbit pulled out of a hat—we marveled: simple, elegant, and yet (therefore?) so hard for anyone else to have done it.

Lawrence Krauss, professor of physics at Arizona State University:
Steve Jobs changed my life forever. In 1983 I was a young postdoctoral researcher at Harvard at a key turning point in my career. I had just won a prize that gave me enough money to purchase my first computer, which I needed to move forward, to write my first book—one I could travel with if possible, but I was studiously ignorant about the existing cumbersome devices, as even portable computers were nothing of the sort. I didn't relish learning some artificial commands and typing on a 5-inch screen. Then, in January 1984 the Mac arrived, and my world changed. I put my name in the lottery at Harvard, and a month later I had the 26-pound "portable" wonder machine, which I proceeded to carry everywhere with me, showing it proudly to anyone who was willing to sit and listen. Apple consistently demonstrated that form and function can combine together to make technology useful, and life-enhancing by making it more fun, and extending ones abilities to do what would have simply been impossible before. I must have sold a lot of Macs in my life, as I continued to remain loyal, and ultimately have owned almost every one of the new machines over the past 27 years. When I moved to Yale as a professor I even convinced our entire group to buy NeXT computers rather than the clunky VAX devices then used by the rest of the department. I am typing this on my MacBook Air, and I marvel at its design and delight in the thought that one man with a good idea, and the determination to carry it to fruition, can make the world a better place. Thank you, Steve. I will miss you.

Gordon Bell, computer engineer, researcher at Microsoft Research:
After my heart attack in '83, [Steve Jobs] invited me to come to Apple…unfortunately, I wasn't ready for the intensity.

I attended various product introductions and was just stunned every time with his performances. I regret not being able to know and interact with him.

A few comments come to mind:
1. Steve is there with Edison, Ford and Watson as an industry creator.
2. We all aspire to make just a fraction of his many contributions to computing—he's right at the top of my hero list.
3. Almost no one living can claim so much—entrepreneurial businessman and leader, demanding and uncompromising designer, and industry creator.

Everyone in computing mourns his passing.