I love to monitor my system. It's one of the things that I can spend my time doing. Not hours of time but I can just stare at the system monitor for like 5 minutes and observe and study which processes are taking most system resources and which processes are playing nicely. That's all nice and good but the most important thing for me to monitor is the bandwidth of my internet connection. It is a BSNL EVDO wireless data card. So the internet speed is not constant and it can vary from 10 kbps to over 200kbps of download speed. And the intriguing part of it is that if you move it just a couple of inches it can have dramatic changes in signal strength and it can change the download speed from 50kbps to 100kbps and vise versa.
So ranting aside, what I really want to talk about is Conky. It's a nifty little system monitor that can render itself right over your wallpaper or in my case just plain old black color(i have set it as my wallpaper:)). So you don't have to start any special application to monitor your system. And the good part about is it doesn't only monitor your system but you can also display the output of any terminal command in it. So the things you can display on you desktop are only limited by your imagination and your scripting or Google searching skills.