Years ago, the only computer I had access to was an Apple II.
I spent a lot of time hacking on it in BASIC, but we eventually
got a 386 before I got into serious programming.
I do still own an Apple system, and still create projects on it
when I have the time...
upload_slow.c. A program to upload
programs slowly from Linux to the Apple II monitor over a super-serial link.
I plan (hope) to make an ARM accelerator card that runs Linux
that plugs into the Apple II, much as the z-80 cp/m cards did
back in the day. (Turns out someone else has managed to do this
before me, but I still might try it anyway).
You can watch a video from 2018 at Kansasfest where I describe
a lot of the above work:
Other Interesting Projects (not by me, and links severely out of date)
Linux
x86 Apple II emulator: I actually got SDL support for an older
version of this. Sadly someone else was already working on it (but
nothing came of it) and I lost my series of patches.
Lunix Next Generation
A unix-clone for 6502 computers. [Mainly Commodore at this point, but I'd
like to help on the Apple II port someday].
Contiki Operating System
Another cool OS for older machines, including the Apple II. Includes
info on people who made an ethernet card for the Apple II.