I have been creating a listing of citizen science apps. Here are a few of them.
1. iBats - Allows for the recording and monitoring of bat calls.
2. iNaturalist - Citizen Science data collection. All of the accumulated information goes into the Global Biodiversity Information Facility for use in better understanding the range and populations of species.
3. Leafsnap - An electronic guide to leaves of trees currently expanding to cover all the United States but for now focuses on trees in the Northeast and Canada.
These are just a few I've found, what are some of your own?