I found that if I have a list in front of me it would be very easy for me to pick the tasks that were most appealing and not the one that needed to be done right now. So I minimized that risk by applying the single task todo list.
The system is simple: You have only one task in front of you. This task is displayed in big bold letters and it won’t go away until you are done with it. Once you are done then the next item comes around. Eventually you’ll finish your todo list in the order you need to do it. it’s very rewarding when you see an empty message in front of you!
So, Tasks is a simple Todo manager that focuses on doing one single thing at a time.
Tasks supports Windows and comming soon Linux and Mac.
Windows
Supports Windows XP, Vista and 7.

Download Tasks for Windows
Linux
Supports the Gnome desktop.

Download Tasks for Linux (comming soon!)
Mac OS X
Supports the Leopard and Snow Leopard.

Download Tasks for Mac (comming soon!)