At least with HN, there's an old mirror. https://github.com/wting/hackernews There's quite a bit of old code floating around out there (even for Zork iirc), of course there's newer code being written all the time (as you know :)).

Besides code I'd also wish for accompanying code reviews and deep dives, like Fabien does for game engines, though for smaller things the code is usually just fine to just dive in and explore.