SliderNav is a JQuery plugin that lets you add dynamic, sliding content using a vertical navigation bar (index). It is made mainly for alphabetical listings but can be used with anything, though longer words can look a bit awkward. The plugin automatically adds the navigation and sets the height for the object based on how tall the navigation is, in order to make sure users have access to the entire list. It also use the overflow: auto; property for the actual content so you can use your mousewheel to scroll through the content as well.
The plugin has been tested (and works fine) on Firefox 3, Chrome 5, IE7, Safari 4 and Opera 10.