I added a list of recommended libraries to the ActivityPub developer guide:

https://codeberg.org/ap-next/ap-next/src/branch/main/guide.md#libraries

- activity (Go, used in GoToSocial)
- Fedify (JavaScript, used in Hollo and Ghost)
- Fedipub (Ruby, used in Manyfold)
- activitypub_federation (Rust, used in Lemmy)
- APx (Rust, used in Mitra)

This list only includes libraries that are actually used somewhere. Libraries that are not used, or used in projects with too few users are not included.

#fedidev #activitypub

@silverpill@mitra.social there's also one in Elixir: https://github.com/bonfire-networks/activity_pub