cpufreq-selector - Is a tool that can be used to set CPU frequency
Use the cpufreq-selector to set the cpu to either powersave or ondemand mode, and you will save power.
These tools can be used to monitor and tweak your power settings at a more advanced level. For instance, you can disable hard drive activity when you're not using it. This is just one example of the kinds of power saving things that you can do with Laptop-mode-tools.
Another great tool for extending battery life, is the package pm-utils. This tool provides shell command line tools to suspend and hibernate your computer
Linux - Extend your laptop's battery life - kioskea.net
Power and Sleep Management - askubuntu.com
manpages.ubuntu.com/manpages/ - hardy (1) cpufreq-selector.1.gz
Corridor Nine - CPU frequency indicator and DIY merchandise
CPU Frequency Scaling - wiki.archlinux.org/
Laptop Mode Tools 1.62 Further Improves Battery Life - news.softpedia.com/
Laptop Mode Tools - http://samwel.tk/laptop_mode/