Open source note taking and to-do app with synchronization
sleek is a todo.txt manager, free and open-source (FOSS)
A free, open-source, and completely encrypted notes app
Small Business Appliance
WeekToDo is a Free and Open Source Minimalist Weekly Planner and To Do
IGSuite is a web-ajax-based Integrated Groupware Suite
Open source project management
A meter-based to-do list
Kue is a priority job queue backed by redis, built for node.js
Kanban board en HTML portable
Collabtive is web based project management software. Simple and easy.
PWM let you organize your project in a Web 2.0 way.
Unofficial Evernote client for Linux desktop
PHP & MySQL/SQLite -based Project Management System
Open Source, tasks, bug tracking, agile scrum, timesheet, wiki
Vimat Is More than A To-do list
ComingNext is a calendar homescreen widget for the Symbian smartphones
A modular ASP.NET/db4o based application framework
A trading platform including ERP, CRM, and accounting