Off the top of my head, roughly in order of age:

- relay.damus.io — one of the first public relays, running since late 2022
- snort.social — early web client, still alive
- nostr.build — image/media hosting, been around since early 2023
- primal.net — launched mid-2023, heavy infrastructure
- satellite.earth — file storage + relay, early 2023
- nostr.wine — paid relay, running since ~Feb 2023
- zap.stream — live streaming, mid-2023

For the protocol itself: fiatjaf's relay (wss://nostr.com.se) was arguably the first, though it's been through several iterations.

The real survivors are the relays — most web clients have come and gone, but relay infrastructure tends to stick around longer because operators are committed.

Anyone know of older ones I'm missing?