It doesn't sound like much of a request nowadays, but up until fairly recent times, there was literally nothing that fit the bill.
In the old days we were dependant upon an extremely expensive 3/4" video editing deck owned by the art school we attended. This machine was capable of recording separate audio and video tracks, and more importantly, able to capture a single frame of video at a time. Hooked to a camera stand, it allowed us to create pencil test animation. (See main menu-Toons/Pencil tests.) At least we got to animate, but it was near impossible to create anything that looked finished, without going the added (ridiculously expensive) route of preparing finished color art work, IE: painted backgrounds and painted clear acetate animation cels. Such a setup is simply not feasible outside of a major animation studio.
Computers always seemed the logical route, but even these we tend to take for granted today. When I did my first computer animation in 1989, any system that was beefy enough to handle color graphics and animation, was still outrageously expensive. Systems that today would only be suitable as doorstops cost in the neighborhood of $5,000 and up.
Mike bought an expensive video deck in the early 1990's called a Lyon/Lamb pencil test system. It had frame by frame recording, but no flying erase head. Therefore in order to shoot a complete project, you had to do so IN ONE SITTING! You couldn't start and stop shooting animation as you pleased; if you stopped recording frames and started again, you'd get a nasty video glitch between the start/stop points. So we had to do all the animation first, test individual scenes, and then have crazy marathon all-day shoots of entire projects. One glitch or mistake in shooting (which is likely when shooting stacks of animation) would screw up an entire production. It was an insane way to work!
Later on, Mike got an Amiga, and he managed to do some animation with that. I experimented with any Mac or PC I could get my hands on, but for the longest time, creating animation with them was hit and miss.
Flash-forward (literally) to today, and Flash is pretty much exactly what we were dreaming about all along. It's like having the most powerful multi-plane animation stand and frame capture system ever devised, all on your desktop. Keep in mind that most Flash animation you see on the web has to be compromised somewhat in order to keep it a downloadable size, but the program is capable of producing stunning broadcast quality output for film and video. Many new TV animation productions currently in Hollywood are being done entirely in Flash. The beauty of this is that actual in-house animation is returning to LA studios. This is an industry that has since the early 1980's shipped virtually all of its animation production overseas to the orient. The fact that some of this can now be stemmed with in-house Flash production is nothing short of miraculous.
Anyhow, I'm just amazed at how versatile this application is. Anyone who is interested in doing animation should learn Flash. I envy the current young generation that will grow up with incredible tools like this readily available. It'll be amazing to see what the next generations of creative folks do with all the technological advances they are growing up with.