Graphing Calculator Users Gallery
There's a long story here. My perspective is that when Apple moved from its 68K Motorola chip to their "hot" RISC PowerPC architecture, they introduced a new mini-app -- the graphing calculator. They made a fuss about it. At the time it reminded me of Mathematica, except even then Mathematica cost hundreds of dollars and this far simpler app was a freebie. It persisted through all of Classic, but vanished after OS X came out.
Now the story of how it came to be, and not be, has come out. And, amazingly, it's back. There's a free version for OS X (works fine in my limited testing) and a $60-$100 commercial version with more features. There's even a book.
I used Mathematica quite a bit 10 years ago, and this is no Mathematica, but I must say it's a very cool tool. I don't do enough math now to judge how useful it would be to an engineer, but it does look like it'd do the job for high school math -- and it's not at all expensive.