I've found that forums seem to provide much of the knowledge previously transferred through Geocities. Detailed, human, non-encyclopedified information about almost anything is available spread through a vast quantity of subject-specific forums across the Internet rather than across webrings hosted on Geocities and the ilk.

I think part of the reason for the shift is that forums have gotten much more advanced: most include a personal homepage, photo gallery, and provisions for making "uber/FAQ" threads that easily surpass the most meticulously curated Geocities sites.