this and geezer's site are the OGs of OS dev. Both offshoots of alt.os.dev, iirc, and have been around for more than a decade.

if I were messing with OS dev today I would probably study the algorithms in a friendly HLL, there are some texts that use Java. these sites are more helpful to actual implementors, specially driver developers.

x86 architecture is terrible for pedagogy in many ways, and it's probably harder today than it was 10 years ago, with real-mode now finally gone, except for the first few nanos after machine boots.