Ubuntu has a laptop-mode-tools package, which is installed by default on laptops. However, laptop mode is disabled by default in Ubuntu Edgy (6.10), because some people have been experiencing hangups with it on certain laptops (mostly Thinkpads). Until now, nobody has any clue what is happening here. To reenable laptop mode, edit /etc/default/acpi-support and set ENABLE_LAPTOP_MODE=true.
If you want to use the latest version of laptop mode tools, you can use the Debian packages, they are compatible enough to work out-of-the-box on Ubuntu. In fact, I would definitely advise using these packages --- the Ubuntu packages are crippled so that some options don't work, the most notable of which are ENABLE_LAPTOP_MODE_ON_AC, ENABLE_LAPTOP_MODE_WHEN_LID_CLOSED and DISABLE_LAPTOP_MODE_ON_CRITICAL_BATTERY_LEVEL.
Install Laptop Mode Tools on ubuntu
Make sure you have a kernel that supports laptop mode. Any version starting from 2.6.6 should do, or any version that includes the file /proc/sys/vm/laptop_mode.
Now you need to download lastes version of .deb package from here
Once you have deb package you can install by double clicking on that or run the following command from your terminal
sudo dpkg -i laptop-mode-tools_1.47-1_all.deb
If everything went OK, laptop mode will be activated automatically the next time you unplug your laptop from the mains (except when you have an APM laptop). You can configure laptop mode tools using the config file, which is in /etc/laptop-mode/laptop-mode.conf. You can read more about the configuration options using