Vannevar Bush, who conceptualized information technology in the 1940s (as opposed to mere computing: computers then were just meant to perform calculations). Douglas Engelbart, who invented the graphical user interface as we know it. Cf. the mother of all demos from 1968, (watch)
What I find interesting is that few science-fiction authors came close, if at all. Some did, but rather more recently. In fact it's rather telling that David Brin is considered prescient for his novel Earth that predicts a number of things (such as blogs) rather astutely ... but that was in 1990.
Take the mobile phone as a more specific example. Almost nobody thought about it. Except possibly Star Trek. Star Trek TNG invented the iPad. I find it interesting that it took that medium to come up with practical inventions, probably because, unlike book authors, its writers had to ask themselves how it would look like when people would interact with higher technology.
We could ask a more general question. Who in history predicted technological progress? The question is historically more profound than it may sound, in that it requires a concept of progress that is so pervasive to our culture today that we have trouble relating with those in our past who did not have it. Instead, the common theme was that of the long lost golden age.
Luhn's seminal paper from 1958, "A Business Intelligence System", predicted in many ways how information is disseminated today. From the abstract:
An automatic system is being developed to disseminate information to the various sections of any industrial, scientific or government organization. This intelligence system will utilize data-processing machines for auto-abstracting and auto-encoding of documents and for creating interest profiles for each of the “action points” in an organization. Both incoming and internally generated documents are automati- cally abstracted, characterized by a word pattern, and sent automatically to appropriate action points. This paper shows the flexibility of such a system in identifying known information, in finding who needs to know it and in disseminating it efficiently either in abstract form or as a complete document.
It's a bit hard to say if he predicted these systems or made they happen because of his work at IBM, but I think it does count, especially since his ideas are still relevant and fruitful.
Some sources:
Nikola Tesla did predict something very similar to the Internet in 1900, with the World Wireless System.
Huffpost article: "Did Al Gore Invent the Internet? No, Nikola Tesla Did"
World Wireless System Wikipedia page
Extract from a 1908 article published in "Wireless Telegraphy and Telephony" magazine:
"As soon as completed, it will be possible for a business man in New York to dictate instructions, and have them instantly appear in type at his office in London or elsewhere. He will be able to call up, from his desk, and talk to any telephone subscriber on the globe, without any change whatever in the existing equipment. An inexpensive instrument, not bigger than a watch, will enable its bearer to hear anywhere, on sea or land, music or song, the speech of a political leader, the address of an eminent man of science, or the sermon of an eloquent clergyman, delivered in some other place, however distant. In the same manner any picture, character, drawing, or print can be transferred from one to another place. Millions of such instruments can be operated from but one plant of this kind. More important than all of this, however, will be the transmission of power, without wires, which will be shown on a scale large enough to carry conviction."