Using GNOME Do is simple enough. Use the meta key (usually the Windows key on most keyboards) and the spacebar to bring the search box to the front, then type in what it is you’re looking for. Looking for a directory? Type in “home” (for example) and GNOME Do will pop up your home directory. Looking for a document? Type in the name and as you’re typing GNOME Do will find documents with a similar name. When you’ve found the one you want hit the enter key and it will launch. The same is true of website URLs.
As you type in your query GNOME Do will pop up the options available to you. There is also a drop-down menu for when there is more than just one possible answer. Click elsewhere on the screen and GNOME Do goes away.
When installed GNOME Do instantly has access to Firefox favourites, applications and configuration tools on the Ubuntu desktop. There are also a good handful of plugins available for doing things such as playing music, accessing instant messaging tools and more.
Ideally Gnome Do is designed for the Gnome desktop environment but there are good reports of it working on KDE and Xubuntu as well.
Installing GNOME Do is very simple in Ubuntu:
First, add the following lines to your /etc/apt/sources.list file
deb http://ppa.launchpad.net/rharding/ubuntu gutsy main deb-src http://ppa.launchpad.net/rharding/ubuntu gutsy main
If you’re running Hardy Heron then change gutsy to hardy.
$ sudo apt-get update && sudo apt-get install gnome-do
Once that is done you’re ready to go … or Do!
Launch GNOME Do from the Applications -> Accessories menu.
(source from : "http://www.tectonic.co.za" by Alastair Otter)