To-Do-O is a simple, cross-platform To-Do List organizer. To-Do-O is available for a wide range of platforms: Linux, Mac OS, Windows, Symbian S60 3rd Edition FP2 and up (5th ed. etc.), and Maemo Fremantle (N900).
The user interface is optimized for mobile devices. The main view shows the To-Do entries organized in a simple tree view. Further features are, e.g., functionality to sync different To-Do-O installations via WLAN and options for automatic marking, moving, and deletion of entries. The desktop version also features a widget that can be freely placed on the desktop and shows the most important unfinished entries. The sort order etc. of the entries shown in this widget can be configured by the user.
The To-Do-O homepage is hosted at sourceforge: http://to-do-o.sourceforge.net/
To-Do-O can be downloaded directly from: http://sourceforge.net/projects/to-do-o/files/