I really like how https://lobste.rs/ uses tags for easy topic filtering.

I'd love to see a system that does automatic topic/trend clustering, along side the manual social bookmarking bits. That would be a killer app for attention economy management. Then give the topic or trend or whatever tags (insightful, humour, etc?) dash/wiki pages of their own with Linked Data additions. Or do the automatic clustering after a page reaches a certain number of upvotes or saves.. 2p anyway..