Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists. It grew out of a frustration that most task managers do not provide facilities for composite tasks. Often, tasks and other things todo consist of several activities. Task Coach is designed to deal with composite tasks. In addition, it offers effort tracking, categories, and notes. Task Coach is available for Windows, Mac OS X, Linux, and iPhone and iPod Touch.
Get it here —> Task Coach