I really, really like Are.na.

I cannot recall how many hours I've spent there going deep into some rabbit hole, browsing pictures of old Sony devices from the 90's.

The only reason I stopped using was because, like many modern apps, I couldn't get over how slow it got over time. I wish someone built a mix of Pinboard and Are.na, where you could save your things - including media - privately and explore what other people have been creating, while still being fast.