Pin a div element to the side
The easiest way to explain what I'm looking for is to show you. So, have a look at www.waldenponder.com. You'll see that on the right hand side there I have a Follow Me twitter element. As you scroll down, the element is pinned to the side of the page.
I've done my Google searching but am finding mainly sticky headers and footers which is not what I'm interested in. Basically, I just need to float a single div along the side of my content.
Any help is appreciated.