Mine is mapping. I am a big OpenStreetMap contributor and I have mapped many towns near me that were previously completely unmapped.
i upload photos i take of plants, birds, mammals, reptiles, fungi, and bugs. The observations (photos + location + annotation) are uploaded to a public database accessible to researchers and universities.
I’ve been involved in multiple species range expansions, and i’ve documented both endangered and invasive species. Pretty fun!
The Android app is very good. The iOS app is good for uploads, but lacks a lot of browsing features like search filters and phylogenetic trees. If you are on iOS i suggest using it in a browser except for observation uploads
You can also upload audio recordings for bird and bug sounds. It’s amazing what you can learn about your local ecosystem!
I love iNaturalist. I lived out in the woods for several years and would see so many different bugs that I didn’t recognize. So when I discovered it about 2 years ago, I started taking pictures of every bug I saw and uploading them to the app to learn what they were. And then in August last year there was an unusual explosion of mushroom varieties in our yard. That’s the one area where iNaturalist is a little weak as it really struggled to give me good ID’s for a lot of them. But it should only get better with time.
I’ll see if I can find some mushroom photos to share here.
Edit: one of my favorite mushroom pics I got during the mycological explosion:
Nice! I hadn’t heard of iNaturalist. Over where I live most people use observation.org