If you're using the GNOME desktop environment in Linux, then consider adding more bells and whistles in it with this great repository of desktop eye candies. Visit http://gnome.org/ for more info on GNOME.
GNOME-Look.org is a fantastic site. It has everything you will ever need to customize your GNOME desktop. However, you should use caution when downloading software from external sites (as usual). I've found that a few of them come from sites that implement tracking cookies.
Other than that, GNOME-Look.org is a very useful site. A must for any user using the GNOME desktop environment.