Xfce long-time users may already know the Xfce Goodies Project, but I just came across it looking for some plugins. Browse through the panel plugins, lots of interesting stuff to get. I installed xfce4-cpufreq-plugin, xfce4-sensors-plugin and xfce4-weather-plugin with aptitude, they are in the Ubuntu repositories, some in universe. All the other items are in the default Xfce desktop install, you have to add them to the panel, though.
