BitNami Tracks Stack is an all-in-one cross-platform installer for Tracks, a Web-based application to help you implement David Allen's Getting Things Done methodology. It installs Tracks, Ruby On Rails, and everything else necessary to have a running program in minutes. It works on Windows, Linux, and OS X.
Chandler is a standards-based "Note-to-Self Organizer" designed for personal and small-group task management and calendaring. It consists of a desktop application and Chandler Hub, a free sharing service and Web application. You can also download and run your own Chandler Server.
The Darwin Calendar Server is a standards-compliant server that allows multiple users to collaboratively share calendaring information. It provides a shared location on the network to store schedules, and allows users to send each other and manage invitations. In order to provide interoperability with multiple calendaring clients, the server implements the CalDAV protocol, which is an extension of WebDAV, which is in turn an extension of HTTP.