The first thing I install on my new Macs is this utility. I love it and had bought it a couple years ago for all my Coaching & Support Members.
Go to this Page and the top great offer is for RapidWeaver (Awesome for creating websites). Go to the offers below and click on the IStat Menu Promo. Save 38% on it for four more days!
Here is a shot of the upper right of my desktop. You can see the iStat Menu items in the Menu Bar. If you click on any of the icons, you get a detail drop down like this one of my fan speeds. (click to enlarge)