This is my version of an LED CPU meter using the parallel port hardware. This allows for up to eight LEDs with no exotic hardware or anything really expensive. I modified the source of a project I found on the web and you can download and play around with it.

I have seen several different methods for calculating the CPU usage and I'm going to change the one I'm using. I will take the number from /proc/stat for the CPU usage and average it over the past user configured number of seconds. Ought to be fairly straight forward.

You can find a good description of some "safe" hardware and a Windows client at the Point of No Return. Hmmm... link is down, looking for a new site with good plans. Maybe an Instructable...