Before the blog took off, before Tumblr became the face of fandom, but around a year after Geocities launched as a platform for Justin Timberlake fan sites, there was The Wiki. We looked upon The Wiki, and we saw its potential as a platform for crowdsourcing knowledge, collaborating, and educating. We saw that it was good.
Then Wikipedia was founded at some point, and the rest is history.
I love well-maintained wikis to a fault. Wikis have been a large part of my continuing education in web design, random trivia, and the minutiae of video game mechanics for a long time, now. Anyone who learns stuff on the Internet owes a lot, directly or indirectly, to wikis and their less-community-oriented cousin The Knowledge Base.
Even though many of the publicly available wiki software options are dated and confusing to operate and organize, they continue to power much of the educational portion of the web.