My musings about my earliest memories of computers brought me back to 1976 and the appearance of the COSMAC ELF in Popular Electronics. I was only twelve, and probably had only the vaguest understanding of what such a machine could do, or why I might want one, but I remember reading these articles and it capturing my imagination. It probably laid the ground work for my continuing fascination with computers. Still, I never really developed any serious understanding of the architecture.
Now, when I stare at datasheets for the 1802 processor, it doesn't seem particularly hard to understand, but it's a pretty peculiar little chip. Wikipedia has a good introduction. It found some significant usage aboard satellites and space probes, including aboard the Galileo probe. You can get more documentation here. While the processor is not well known now, it actually generated significant interest until the 6502 hit the market.
I've just begun to dig around for more information:
Addendum: There is a huge pile of RCA 1802 code on archive.org. Judging by the filenames, not all of it is 1802 related, but there is a ton of stuff.