This Wired article also mentions the Canadian Roberts variation. When I was living in Canada, I remember being annoyed at having to buy special screwdrivers for furniture that I bought there. I actually came across a set of Roberts power tool heads that someone had thrown into a gutter. True story.
F. Phillips receives patents for a new kind of screw and the new
screwdriver needed to make it work. It changes the worlds of mass
production and machine repair, not to mention your home toolbox. (Randy Alfred, Wired)
Other, screw-related blog entries: