Building on the Fediverse is hard. Here is a list of ActivityPub and other developer resources that have been helpful in developing Emissary.
This is not a canonical or official list by any means, but hopefully this list of bookmarks is valuable to others who are building their own Fediverse apps.

A federated wiki the focus on fighting Wikipedia from a developer of Lemmy. I don't like their cause, but I'm interested in the technical aspect (I myself had been trying to come up with an excuse for using ActivityPub for wikis for two years). They seem to use WebFinger usernames like that: article@server! Wild! Their treatment of media is unclear to me right now, also they seem to federate Markdown, which is just ridiculous for a Wikipedia killer. Wikipedia uses infoboxes a lot, how are you gonna replace that?

Fediverse Enhancement Proposals

A selection of Webfinger files as produced by common Fediverse apps

Where ActivityPub developers coordinate their efforts to make the Fediverse a great space for cooperation

A forum for the fedidevs. What's funny is this notice it shows on my outdated Safari:

Unfortunately, your browser is unsupported. Please switch to a supported browser to view rich content, log in and reply.

This sentence contains to a funky website that recommends some browsers. Links2 is not there for some reason.

I should join the forum though, as I'm a proud fedidev now!

P2P technology is doomed on mobile [because of small batteries]. For a democratic web, we need to work on federation.

The author thought so in 2016. 8 years later I'm developing for the federated web, cool. I like how they mention Diaspora, which is history now.

huh, tedu had something like betula for idk 5 years already and ive only learned that??

Turn Mastodon into your feed reader

This is the codebase for castling.club, an ActivityPub server with a single
hardcoded 'King' service actor that acts as a chess arbiter.

Opt-in Fediverse search. Users individually can join too.

A basic Mastodon client for Classic Mac OS

After four years, Honk 1.0 is released.

Make sure to read the source code, it's comedic:

• https://humungus.tedunangst.com/r/honk/f

An open-source activitypub network and fediverse database, powered by FediDB

Somebody proposes something like a federated wiki. I'm skeptical.

Agora is mentioned in the thread!

StreetPass is a browser extension that helps you find your people on Mastodon.

Now available for Safari.

A five-year old overview of Fediverse history. It tells us about older exodi from the siloœ. How fun! We exile en masse, but the silœ still stand. How come?

The author predicts that the future belongs to ActivityPub. Yeah, kinda.

My philosophy is that (nearly) everyone can and should host their own microblog, but I’m less convinced that’s true for a link site.

My philosophy is totally different.

Main instance:

• https://azorius.net

This project is meant to run as a standalone service to deliver posts from your own website to ActivityPub followers. You can run your own website at your own domain, and this service can handle the ActivityPub-specific pieces needed to let people follow your own website from Mastodon or other compatible services.

Fediverse Network Statistics

Mastodon is the biggest with big leap. Second is Lemmy (wow! big growth). Mastodon has 7.5 mln users, Lemmy has 622 k usrs. Misskey has 328 k users.

Kitsune is a microblogging server that utilises the ActivityPub protocol to connect your instance to a global interconnected network.

Not only can you speak to other Kitsune users through it, you can also connect to people using software like Mastodon, Misskey, etc.

This person develops tools for the Fediverse in Go.

Link aggregator inspired by reddit and hacker news using ActivityPub federation.

via https://t.me/dcntr/2122

A Social Feed Reader for the IndieWeb

The Mac version simply didn't run. I installed the Android version. On first run it showed a quick error which I did not understand. I wanted to see how my Betula, which emits h-feed and h-entry microformats, would look like in this app. Turns out, when it talked about IndieWeb, it talked about MicroSub, not microformats2. What a liar!

I tried to authorize to https://merveilles.town, after all it supports Mastodon too! It failed to authorize me.

Overall, I couldn't do anything at all with the app. Sharing it nevertheless.

TL;DR: Lemmy is bad: it does not delete messages and the author is bad too.

Go bindings to the Lemmy API, automatically generated directly from Lemmy's source code using the generator in cmd/gen.

An ActivityPub proposoal for pinging

An extension that brings XWiki to the Fediverse

No, not really, for

blogs with RSS/Atom/JSON feeds are already interoperable

/kbin is an open source reddit-like content aggregator and microblogging platform for the fediverse.

Create and moderate communities, meet people with similar interests, and develop your passions.

Classic VK-inspired.

Author's instance: https://friends.grishka.me/

Contains quotes from Christine Lemmer-Webber!

Guppe brings social groups to the fediverse — making it easy to connect and meet new people based on shared interests without the maniuplation of your attention to maximize ad revenue nor the walled garden lock-in of capitalist social media.

I used to post to https://a.gup.pe/u/mycorrhiza.

This project represents a new attempt at the social link aggregator service. It is modelled after (old)Reddit, HackerNews, and Lobste.rs trying to combine the good parts of these services while mapping them on the foundation of an ActivityPub generic service called FedBOX.

It targets small to medium communities which ideally focus on a single topic. At the same it allows the community to reach other similar services and the rest of the fediverse ecosystem through the ability to federate.

feediverse will read RSS/Atom feeds and send the messages as Mastodon posts. It's meant to add a little bit of spice to your timeline from other places. Please use it responsibly.

A federated forum / link aggregator using ActivityPub.

Pleroma creator's blog.