An Open Source & Simplified To-Do List Application: Hub List
Hub List is an open source to-do list application that works on the desktop.
It has versions for Windows, Mac OS X + Linux and a mobile one that mostly targets the iOS platform.
The application supports creating folders>sub-folders and tasks>sub-tasks for an unlimited hierarchy.
Hub List is currently in beta status and working on impressive features like auto-synchronize data to any private cloud, collaboration and importing-exporting data.