Out of a desire to never have to add this to a theme again I whipped up a little plugin – its really simple. The plugin adds a little ‘scroll to top’ button to your website. All you have to do is download, install and activate the plugin. That’s it. When you visit your website, you will see the little button on the bottom right of the webpage allowing users to scroll to the top of the screen.
You can download the plugin here: http://wordpress.org/plugins/back-to-top-scroller/