GNU Health - GNU Health is a Free/Libre project for health practitioners, health institutions and governments.
Kareo - Kareo - Go Practice | Medical Office Software for Small Practices
OpenMRS - OpenMRS is a community-developed, open source, enterprise electronic medical record system platform.
drchrono - An EHR built for your specialty:
CureMD - CureMD is the leading provider of innovative technology and medical billing services that transform the administrative and clinical operations of healthcare organizations.
Solismed - A free clinic management system designed for use by independent practices and free clinics. It's designed to automate your business operations and help you get things done more quickly.