Obviously wikipedia.org. Nothing better has been invented in 20-some years. I honestly feel relief when I research some topic and it has Wikipedia page on it, so I don't need to dig through some sh**y blogposts
Edit: I mean: it's one of the very few websites that actually provides sources of information. It's insane it's that rare these days. And most important facts are just placed in visible and easy to spot place, no need to dig through author's life story, thanks for subscribers etc. before getting to the point.
This is more of a testament to HTTP/HTML though. It's a universal format for storing and retrieving information.
OpenStreetMap is, along with every other geo data project, limited by the common coordinate systems we have for storing and retrieving geospatial data -- and these are almost always planetary, not universal.
I will agree, with an additional caveat that I particularly like the Simple English Wikipedia quite a lot (simple.wikipedia.org) if I need a quick understanding of a topic.
Edit: I mean: it's one of the very few websites that actually provides sources of information. It's insane it's that rare these days. And most important facts are just placed in visible and easy to spot place, no need to dig through author's life story, thanks for subscribers etc. before getting to the point.