Indicator-CPUfreq is a modification of previous CPU speed switching applet comes with Ubuntu 10.10 and older. The applet written by Артём Попов can be used in Ubuntu 11.04 to change and monitor CPU speed due to Gnome panel will be going away.
The applet provides 4 modes: Conservative, Ondemand, Performance, and Powersave. It is useful especially for Ubuntu Laptop to delay the use of battery while working outside.

Install

To install the applet, open up a terminal window from Applications -> Accessories menu and install from Artem’s PPA:

sudo add-apt-repository ppa:artfwo/ppa
sudo apt-get update
sudo apt-get install indicator-cpufreq

Alternatively, click following link to choose the latest indicator-cpufreq and download an appropriate package in its drop-down menu.

Indicator-CPUfreq in launchpad.net

After installation, press Alt+F2 and type “indicator-cpufreq” to launch the applet, you can also make it launch at every log-in by adding it to System>Preferences>Startup Applications.