CPU Frequency Scaling Monitor

If you want to prolong the battery time on the laptop you have to make the CPU use as little power as possible. This can be done by forcing the CPU to run at its lowest clock frequency. By default Ubuntu uses the Ondemand frequency scaling policy, and you have no control over that. The CPU will alternate between 2 to 3 different clock frequencies depending on the CPU load.
If you follow this howto you can get control over the clock frequency scaling policy of your CPU with a few mouse clicks.

You can enable the applets full potential by doing one of the these:

1)
Change the permissions on the program cpufreq-selector:
sudo chmod +s /usr/bin/cpufreq-selector

2)
sudo dpkg-reconfigure gnome-applets
and answer “Yes” to the question regarding setting the suid of the cpufreq-selector executable.

If you left click on the CPU Frequency Monitor Applet, you can now select a clock frequency or choose the modes Conservative, Ondemand, Performance, or Powersave.