FontRegister is a command-line, Open Source app to install fonts or repair the font registry.

As always, anything command-line is much more difficult for many to use, so we'd love to see an optional GUI here considering the size of many font collections. That said, it is still a handy, capable tool to manage your fonts including fon, ttf, ttc, and otf.

Currently, the following commands are available:

//Will start a commandline interface:
fontregister
//View all available commands:
fontregister --help
//Perform registry cleanup and font repair:
fontregister --cleanup
fontregister --clear
//Register fonts in the following folders or specific file/s:
//Note: Folders are deep-searched recusively.
fontregister "c:/folder" "c:/font.ttf" "./relativedir/" "./relativedir/font.otf"

Help commands include:

--cleanup / --clear:
Will remove any old font registrations in the registry.
Will repair any missing font registrations for fonts located in the C:WindowsFonts directory(this step
will be skipped for .fon fonts if FontReg cannot determine which
fonts should have "hidden" registrations).
"c:/path1" "c:/font.ttf" ... "./relativedir/"
Will add or replace a font with a given path/folder.
Note: Folders are deep-searched recursively.

FontRegister certainly gets the job done for command-line geeks, and it's good enough to be listed here, but we remain hopeful that an optional GUI becomes available down the road.

Similar:

How to Install or Uninstall Fonts in Windows