Bill Buxton's "Multi-Touch System I have Known and Loved" has been updated as of Sept. 2009. The article provides examples and a history of the multi touch systems Buxton has been involved with or known about over the years.
Multi-touch technologies have a long history. To put it in perspective, my group at the University of Toronto was working on multi-touchin 1984 (Lee, Buxton & Smith, 1985), the same year that the first Macintosh computer was released, and we were not the first. Furthermore, during the development of the iPhone, Apple was very much aware of the history of multi-touch, dating at least back to 1982, and the use of the pinch gesture, dating back to 1983. This is clearly demonstrated by the bibliography of the PhD thesis of Wayne Westerman, co-founder of FingerWorks, a company that Apple acquired early in 2005, and now an Apple employee.
In making this statement about their awareness of past work, I am not criticizing Westerman, the iPhone, or Apple. It is simply good practice and good scholarship to know the literature and do one's homework when embarking on a new product. What I am pointing out, however, is that "new" technologies - like multi-touch - do not grow out of a vacuum. While marketing tends to like the "great invention" story, real innovation rarely works that way. In short, the evolution of multi-touch is a text-book example of what I call "the long-nose of innovation.