GFreqlet is a GNOME applet for Linux that not only monitors CPU frequency scaling, but also allows the end user to change the frequency or governor with just a click. It automatically detects which frequencies and governors your processor supports, so there is no configuration required. The applet itself is not run as root, nor required to modify to run with root ownership, but password prompts with gksudo if a super user action is required. GFreqlet is very straight forward and minimal.
GFreqlet is open source software, licensed under the GNU GPL (General Public License).
This applet was made in Ubuntu Linux 6.10 (edgy), these features worked "out of the box", and only python and python bindings for gnome needed to be installed. This has not been tested on other Linux distributions.
If the CPU frequency scaling governors are compiled as modules, you need to load them first:
$> modprobe cpufreq_performance cpufreq_ondemand cpufreq_conservative cpufreq_powersave cpufreq_userspace
GFreqlet can be downloaded from the sourceforge.net project files page.
Here's a few screenshots of GFreqlet in action.