I just discovered a great little app (do we call desktop software for "apps"?) that easily allows you to monitor your RAM and CPU usage. This simple piece of software places two color-coded bars behind your taskbar - one for CPU and one for RAM. The length of the bar represents the amount in %, and the color gives you a quick idea about how much. For example, orange might be set to represent memory usage between 70-80%.
Check it out if you want! RAM CPU Taskbar.