#PawFed is a project close to my heart. It's a collaborative map for animal welfare that bridges the #Fediverse and #OpenStreetMap.
The idea: mention @PawFed from your Mastodon account with hashtags and a location, and your report appears on the map. No signup, no app, just your existing Fediverse account.
It's not perfect yet, but the foundation is there. I will publish the source code soon under AGPL.