Since moving from Fedora 6 to Fedora 8, I've found I no longer have Nimbus Sans Condensed, DejaVu Sans Condensed, and DejaVu Sans Light. However, when I checked /usr/share/fonts they were there! I've tried moving them to /usr/share/X11/fonts and to .fonts (and running fc-cache), but they are still ignored.

The author of the Libertine fonts says that the X-window system has altered font handling with strange results: you can no longer install the underlined version of Libertine, or it will be chosen instead of the standard one! Could my problem be another side effect rather than a Fedora thing? But why has no one else complained?

I see that there is no fonts.dir file in /usr/share/fonts/dejavu-lgc (why?), but the other DejaVu fonts are still being found, and a fonts.dir file with entries for Nimbus Sans Condensed is present in /usr/share/fonts/default/Type1.

(Wouldn't it be nice if all vector fonts were in one place, in just two directories by type. That'll be the day!)

Any comments or suggestions, anyone?

Have you looked in your xorg.conf file? You should have something that looks like this in the Files section:
You also may need to execute mkfontscale followed by mkfontdir in the individual font directory where your fonts are intalled; e.g., if they were TTF, you'd do this in /usr/share/fonts/TTF (if the fonts.dir and fonts.scale files do not exist in that directory).

http://www.kegel.com/linux/tt.html
The information it this link is a bit dated, but you may be able to adapt the instructions to your situation.