I've learned that I can put .ttf font files in
~/.fonts to use them on Ubuntu.
Which other font formats can I use this way? I'm having trouble finding the right documentation.
Font rendering in most applications is done by FreeType 2.
So mainly, you can use:
From the types that wiki page lists, I know that TrueType and OpenType should work fine. Certain bitmap and PostScript fonts might work, though googling around it seems you may not get anti-aliasing with those.
FontForge fonts can't directly be used, but you can easily use FontForge to convert them. EOT and WOFF fonts can be used indirectly through the browser for the web, but not on the desktop. Other types you may simply have to try and see if they work.