Streaks - The to-do list that helps you form good habits.
Castor EDC - Castor offers you a user-friendly and fully featured application for electronic data collection.
Taskful - Deadlines, meet your match.
GNU Health - GNU Health is a Free/Libre project for health practitioners, health institutions and governments.
ToDoList - Windows desktop application to stay on top of your daily tasks.
OpenClinica - OpenClinica is an open source clinical trials software.