Castor EDC - Castor offers you a user-friendly and fully featured application for electronic data collection.
ClinicMED - Clinic MED, an open source application for Professional Clinic Management licensed under GPL
GNU Health - GNU Health is a Free/Libre project for health practitioners, health institutions and governments.
OpenMRS - OpenMRS is a community-developed, open source, enterprise electronic medical record system platform.
OpenClinica - OpenClinica is an open source clinical trials software.
Med-Quest - Cloud based Clinical EDC with a focus on speed, user interface and collection automation techniques.