I used to have a setting in my .emacs file which enabled the cpu load in my emacs23 status bar. But I don't seem to be able to find the command anymore. It used to be on the emacs.wiki but somehow I couldn't find it. Any ideas?
The system load is shown right beside the time in the status bar. You can display the time when you set the variable display-time-mode to t.
There are a few options you can set, especially Display Time Load Average Threshold (set to 0.1, so load isn't showing up when it is beyond 0.1). You can set these options very easily via M-x customize-group RET display-time RET
There are also some packages for further customization.