This post shows you a cool possibility to keep an eye on all those system parameters.
The most convenient method that I’ve found so far is iStat Menus.
They provide a lot of different plugins for the taskbar and it’s free…

Brightness control
To control the screen brightness I use the Shades application which can be downloaded here for free.

Slimming down your installation Use Youpi Optimizer to delete the languages you don’t need ( Download here – freeware). Don’t forget to just check the languages you don’t need (I kept English and French).
Then to go even further you might use Xslimmer to reduce further (languages and binaries) the size of your OSX installation (Download here – commercial licence)