BBC Micro Elite source code
It covers the original BBC Micro cassette version, the enhanced BBC Micro disc version, the super-fast 6502 Second Processor version, the flicker-free BBC Master version and the cut-down Acorn Electron version, all of which were written by Ian Bell and David Braben and published by Acornsoft. It also includes Elite-A, Angus Duggan's extended version of the original game... More here.
I am sure people who are cleverer than me will find this useful, but I just like it for the memories. Being at the start of that revolution was genuinely exciting at the time.