It's a great pity that the recent growth in interest in DH has come about just as many of these men and women are coming to the end of their careers, or have retired. We, the next generation, benefit from all their hard work but there is a danger that they may not receive the credit they deserve for it. I had the great privilege to work for some of them and to get to know others as part of the digital humanities community. Even if I only confine myself to the UK pioneers, it's still pretty impressive roster. This is also only my opinion, others might want to add different names to what is probably far from an exhaustive list.
I would suggest that anyone interested in how DH really came about should read the first chapter of Susan Hockey's, still very valuable, book, Electronic Texts in the Humanities. This provides a very interesting history of the development of DH. Susan herself was, of course, one of the great pioneers of DH, and my predecessor but one as head of Department of UCL Information Studies (then SLAIS). I regard her as a very important mentor: without her support and encouragement my career could not have developed as it has. I also worked for Lou Burnard when he was head of the Humanities Computing unit at Oxford. Lou also had a huge impact on my career, since this was my first job in digital humanities. He's also had rather a significant impact on the World Wide Web, as one of the leading developers of XML markup.
These are the two innovators in the field that I know best, however, there are others equally important and equally as eminent. For example, Harold Short, who was until recently the head of what is now the Department of Digital Humanities at King's College London (then CCH) did a huge amount to establish the discipline in the UK. Willard McCarty, of the same department is justly celebrated as a leading innovator in, and deep thinker about our field. Other celebrated pioneering UK digital humanists include Mark Greengrass and Seamus Ross who set up the DH centres at the Universities of Sheffield and Glasgow respectively when such things were the extremely rare bastions of what was, for far too long, a rather small and embattled discipline. David Robey has had a vital leadership role in DH, whether for his work as a scholar, or for the Association for Literary and Linguistic Computing and in the context of the Arts and Humanities Research Council. Also at Oxford, Alan Bowman, has also done very important work using digital techniques to aid the interpretation of ancient manuscripts.
Of course Marilyn Deegan, who moved from Oxford to KCL is another extremely eminent DH scholar; an inspiration to women DHers in a field that has always been remarkably female-friendly despite its techiness. Another important female DHer (who nevertheless did not like to be defined by her gender) was Jean Anderson, who worked on linguistic copora at HATII (the Humanities Advanced Technology and Information Institute) in Glasgow, and contributed so much to the ALLC executive.
I tend to regard Andrew Prescott, the new head of DDH as a contemporary of mine since, in common with colleagues such as Melissa Terras, Lorna Hughes, John Lavagnino, and Ann Gow, he is still very much in the thick of shaping the present and future of DH in the UK. Perhaps Andrew wouldn't thank me for saying it, but actually he has a much longer history in the field than I do, given his pioneering work on the Beowulf manuscript.
Thus without looking beyond the UK to figures such as John Unsworth, and the late Antonio Zampolli it's quite easy to compile an impressive list of the genuine DH pioneers, and, as I say, this is just my own selection (Do comment and suggest others, if you'd like to) So if you're new to DH and you haven't heard of the work of the people I have discussed, I'd recommend that you find out about them as soon as possible. Like the man said, those of us in the next generation are standing on the shoulders of giants.