TV Tropes is the definitive rabbit hole: http://www.tvtropes.org For me, a close follow-up is the SCP Foundation: http://www.scp-wiki.net/
I'm a cofounder of All The Tropes, a noncommercial advertising-free fork of TV Tropes: https://allthetropes.org/wiki/Main_Page Because we don't have advertising, we can take a low censorship approach while protecting your privacy. We'd love to have you come on board if you have many hours that you're not using.
What disgusted me was what TVT said in response to ATT. There was a thread essentially claimed it was a weird XXX trope site that was ripping them off: nobody corrected this perception, and nobody even disagreed, despite the fact that looking at the FAQ for five minutes would have made it abundantly clear that this wasn't the case. The mods then said that ATT "didn't deserve any more attention or discussion" and pretty much outright said that mentioning it further was asking for a ban.
It says something about a community when they aren't mature enough to discuss their competitors and legitimately assess them, instead constructing strawmen and saying that anybody who talks about it will be banned: TVT, of all places, ought to know better.