This is PathScrollbarMenu, a javascript implementation of the neat little scrollbar indicator that you can see on Path's mobile apps. It allows the developer to center any content on the scrollbars of a site.

We implemented it at Jetsetter so we could allow users to jump between sections, but still give them the largest content area possible.

GitHub: http://jetsetter.github.com/PathScrollbarMenu/

There is an example page in the project but you can also check it out in action on our new homepage: www.jetsetter.com/?via=hackernewsos