Apple Newton MessagePad
Apple almost invents the World Wide Web
Bill Atkinson's Hypercard, which came out in 1987, was the first commercially successful hypermedia system. It organised data into cards which you could navigate around, or browse, and data in one card could be hyperlinked to data in another. Its very versatility made it hard to market, but a system based on very similar principles was unveiled four years later and did pretty well. That one was called the World Wide Web.
There's a sad irony to the damage the iPad is doing to Microsoft's Windows business, because Microsoft was in the tablet market first. Nine years before Apple unveiled its tablet computer Microsoft had manufacturers making Tablet PCs, portable devices with touchscreen interfaces. They bombed for several reasons - price, Microsoft trying to cram an entire desktop operating system into a tablet; touchscreens that wanted pens, not fingers; bone-headed internal squabbling that meant Office didn't work properly; and battery, touchscreen and wireless tech that wasn't quite up to the job of all-day mobile use. Every time somebody buys an iPad, Steve Ballmer sheds a tear.