[codingdave]

Wikipedia. You can go down some fun rabbit-holes there, and when a topic intrigues you, search engines will take you even farther.

[pknerd]

How to find interesting wiki links? I am interested in science and philosophy.

[jmiskovic]

Wikipedia Portals were built for this.

https://en.wikipedia.org/wiki/Portal:Science

https://en.wikipedia.org/wiki/Portal:Philosophy