To locate research papers that use citizen science data, search for any or all of the following concepts, modified by the scientific discipline for which you're seeking information:
Below are a few open source search engines to get you started. Don't forget the commercial databases (Scopus, Web of Science, etc) that may also be available through your local library. Also check out Citizen Science: Theory and Practice, an open access journal published by the Citizen Science Association.
Monitor Change, a concept developed by Sam Droege of the USGS Patuxent Wildlife Research Center, encourages citizen scientists to monitor environmental and social change using iPhones, photo-stitching, and time lapse.
Nerds for Nature used this idea to monitor how the landscape charred in the Mt. Diablo Morgan fire changed and recovered by taking pictures from fixed locations for one year after the fire.
For data generated by the public to have a meaningful impact, quality assurance during data gathering is critical. U.S. EPA has created the Handbook for Citizen Science Quality Assurance and Documentation to help organizations starting or growing a participatory/citizen science project. The handbook is designed for organizations that are starting or growing a participatory/citizen science project and where transparency in the scientific methods for collecting the data are central to the outcome of the project. The handbook also includes templates and examples.
The Association for Advancing Participatory Sciences has developed a data ethics toolkit and a data standard for public participation in scientific research.
This is a small sample of research papers that use citizen science data.