Here we go (if you click the link above, the article is actually longer, but I took the part that actually does the job and pasted it here):
Adding fonts in GNOME
Saturday, July 25th, 2009
- Go to your home folder
- Enable “Show Hidden Files” option from Nautilus View menu
- Then create new folder with name “.fonts” (with dot in front)
- Now in new folder copy all your true type fonts
- Now restart and new fonts will be in use.