I stumbled across this app a while ago and figured I'd share. If you enjoy finding endangered or threatened species, you can share your findings with scientists and the community as a whole. Sharing information about surviving trees in the wild is a good way to have a small part in preserving our native ecosystems and bringing certain species back from the brink of extinction. TreeSnap
Here's another good site that also has a mobile app to go along with it: A Community for Naturalists ยท iNaturalist