Mastodon is obviously the most famous example of ActivityPub integration.
But what's just as exciting to me is that WordPress, Nextcloud and Gitea are working towards including ActivityPub into their apps.
Certainly, both apps are already collaborative in nature. But once ActivityPub is turned on, they become decentralized *social media*.
That's the real revolution right there.
The possibilities for decentralized social media are endless. Imagine ActivityPub integration with self-hosted:
1. Calendar
2. Presentations
3. Project management
4. Wikis
5. Games
The Internet has now become exciting again!