Gnome Font Manager is worth a look; it's not a professional solution for managing fonts, for publishing or graphic design, but it is a simple application for the basic needs of most desktop users.
Gnome Font Manager (no surprise) designed to work under the Gnome software stack (Gnome Shell, Unity), but as long as you have the minimum Gnome libraries, it will work on other desktop environments including KDE, Xfce, LMDE
To install Gnome Font Manager on Ubuntu, there's the Terminal option:
sudo apt-get install font-manager
Or search for font-manager in the Software Center.
Gnome Font Manager will be installed and accessbile via the Unity dash, or whatever menuing system you have on your desktop, typically under Applications > Graphics > Font Manager.
What you get is the ability to install and unintsall fonts, preview available and installed fonts, enable and disable individual fonts and also search fonts by keyword. RC
Gnome Font-manager home page is at: code.google.com/p/font-manager