System Monitor for Mac OS X

Do you like to keep an eye on your Mac's system resources? Well the in built Activity Monitor may give you a load of information, however it does take up an amount of screen real estate. If you want to see your resources in the menu bar then there is a solution, check out Menu Meters.

Its a very customisable piece of software, you can choose the refresh rate and choose which metrics are displayed and there are even options for each metric. The order which they are displayed can be changed by holding down command and dragging each item.