Parallax is the easiest way to add parallax background effects to your websites. As you scroll pay attention to the background of the above banner. You will notice that as you scroll down the page, the background image is scrolling at a different rate than the content. This subtle effect makes a big difference in making your website stand out.
You can add content into Parallax (like the above banner) or you can simply leave it empty in case you would prefer to have just an accent image between your main content areas (like below).
I know. Parallax is cool. However, I just want to caution you about overusing it. Sometimes less is more.