Castr.me
Castr.me turns a Nostr identity into a podcast feed by collecting the audio and video someone has already posted.
Why it matters
Plenty of people publish audio to Nostr without ever thinking of themselves as podcasters, and podcast apps cannot subscribe to an npub. Generating a feed from what is already there bridges the two without asking anyone to change how they post.
How it works
It scans a profile's kind-1 events — see Nostr Event — for links to media files, and emits a valid Podcasting 2.0 RSS feed where each of those links becomes an Enclosure. A profile that has never posted media produces an empty feed. It runs at castr.me.