TzClock is simply a Cairo clock that displays on your desktop the current local time around the world in an accurate way with support of multiple time zones. TzClock comes also with an accurate stopwatch and many other features like the possibility to customize the appearance of your clock.
To install TzClock under Ubuntu 11.10/11.04, you need first to install this dependency:
sudo apt-get install libnotify-dev
Then compile and install from source with this sequence of commands:
wget -O tzclock-3.0.1.tar.bz2 http://goo.gl/eB3NE
tar jxvf tzclock-3.0.1.tar.bz2 && cd tzclock-3.0.1
sudo make install
Use now the Unity Dash to start TzClock. That's it!