Linux only: Font manager application FontyPython organizes system fonts into "pogs"—easily installable groups of fonts that can be organized on a per-project basis. Getting started with the application is simple—just add the fontypython package through the Synaptic package manager, or use the apt-get command line to install it from the repositories.
sudo apt-get install fontypython
Once the package manager finishes, new system fonts can be installed by adding downloaded fonts to "pogs" and toggling their installed status. The fonts will be symlinked to your
~/.fonts folder from their original location—so you can organize your font collection however you please. FontyPython is free and open source, for Linux only. And now, for something completely different—Windows users can check out previously mentioned AMP Font Viewer.