A while ago I was visiting a buddy who is a TA at the physics department for a state university, and I was stunned to see an Apple //e hooked to a data-collection setup. It was for some kinematics experiment, for an introductory-level class.
Wasn't his idea or anything - many of the experimental setups were inherited from previous staff, and simply left as-is unless something broke. I did some digging later on, and apparently the //e was shipped as the standard interface for certain models of mass spectrometers, some (many?) of which are still in use, //e and all!
Where have you run into Apple II systems that are still in active, productive use? Amazingly, they seem to retain slivers of the foothold they once had in education. I wouldn't be surprised if there were some less-than-spectacularly-financed schools still using IIGS's and ImageWriters to print out banners.
Looking through Flickr just now, here's an Apple II Plus still being used in an office environment as of June 2007!
That just blows me away. It's one thing for the Apple II to survive in education, but quite another to see it still being used by a small business, the key to its early ascent. An a II Plus at that.
I wish I could say that I've seen an Apple II still being used today but they just aren't so common in this country (the UK).
The UK equivalent of the Apple II would be the BBC Micro which I have seen a few of. Before I finished high school (just a year ago) the physics department still used a BBC Micro to do experiments with because it still worked fine and the modern hardware was just too expensive to buy.
This is how I got my start loving macs and apples. My old biology teacher at high school had a room full of IIes he was running his programs on. When I asked why, he said because it still works. Amazing. He even had a few in the "grow room" he kept for spare parts.
This was up until 2005, I don't know what happened when they moved into the new building. Judging by him, though, he fought tooth and nail to keep them. He's in his seventies, and drives from his farm every day to teach at a school in the city.
I have every intention of using my resurrected 1978 Apple ][ for regular use:
classic arcade gaming (playability of some games is still 2nd to none)
possibly some basic file keeping (storing my RC flight data etc)
kids programs (Apple II big "real" keys and colour well suited)
text based adventures (Infocom still rules!)
I will still try to tinker/hobby around from time to time. Speech synthesis, perhaps robotics and that holy grail - connection to the internet.
I've seen lots at local schools, mainly just IIe's and IIgs's, however I once saw (2 years ago a II Plus)... Great for kids, easy to learn too!
I've seen in the 90s apple iis being used for lab work in the electronic industry. There were 3rd party add ons to the iis that could add things like industrial measurement devices (i.e. electric measurement, temprature guages etc). If the machine was still working and doing its job there would be no need to change it. I wouldn't be surprised if hte last most apple iis sold by apple went to some of these companies.
Found another one just today - an Apple //e at a local pawn shop being used for inventory! No pics unfortunately. It was the original '83 model with the white-lettered keytops, and it had a Kensington System Saver fan attached.