I was able to get font thumbnails working by using Saisombun's instructions, then adding the appropriate gconf entries to enable the thumbnailer. The gconf instructions are here:
but they don't explain how to add new entries, something which I have never done before. After a good deal of searching around, I was able to figure out how to use gconftool-2 to add the necessary entries.
Here are the complete instructions to enable font previews in nautilus:
1. If you have not followed Saisombun's instructions to install the gnome-thumbnail-font binary, do that first. They are in the post directly previous to this.
2. Open a terminal window as the user you want to enable font thumbnails for (you will need to enable thumbnails for each user individually).
3. Type the following to add an entry for "application/x-font-ttf" to gconf:
4. Now add the actual command.
gconftool-2 -t bool -s /desktop/gnome/thumbnailers/application@x-font-ttf/enable true
You can specify your own custom preview text by adding the --text custom tag to the gnome-thumbnail-font command (put it before the %i). Here is an example that shows a preview of AaZz instead of just Aa:
gconftool-2 -t string -s /desktop/gnome/thumbnailers/application@x-font-ttf/command 'gnome-thumbnail-font --size %s %i %o'
gconftool-2 -t string -s /desktop/gnome/thumbnailers/application@x-font-ttf/command 'gnome-thumbnail-font --size %s --text AaZz %i %o'