You can try using 'NitroTask'. It is a simple, nice, and very useful To do list management apps.

It has these features, I was looking for a long time:

• Simple addition and deletion of task


• Theme support, include 5 themes. (awesome feature).


• Task synchronization with Dropbox and Ubuntu one (Cool!!)


• Multi Language support


• Sort by Title, Date or Priority. (very handy if you have a long list)


• Custom default background image support. (Can be used for killing boredom)

To install it, use these command by opening a terminal using Ctrl + Alt + T shortcut.

sudo add-apt-repository ppa:cooperjona/nitrotasks

sudo apt-get update

sudo apt-get install nitrotasks

^{This is currently available for Ubuntu 11.10, 12.04 and 12.10}

I think, you will enjoy this software.

Here is a screenshot below: