Ask HN: What is your favourite rabbit hole to get lost in?
Hacker news classics: jsomers.net/hn/ (I downloaded them all and lurk to find stuff interesting then go back to the comments)
Lesswrong, until I learn about roko's basilisk
Comic books.
Nixon tapes
For anyone who hasn't seen Harry Shearers re-enactment of extracts from the Nixon tapes, say goodbye to a few hours:
Malware analysis
How to get started?