One of the many projects I got involved during my first month at grad school was Inhabited Web--the brainchild of my friend Chris. Chris needed some folks with hacking skills to help him bring his ideas to life during a Yahoo HackU contest, so my friend Bryan and I joined forces to help him out.
In short - the system embeds a small, simple visualization into web pages, next to the browser's scroll bar. Triangles are used to represent single users and their position on the current page (scroll position). Collectively, this allows you to see where people are congregating on a web page - perhaps next to a great deal, interesting news story, or funny video.
To our surprise, our team won the contest and an all-expenses-paid trip to show off our work, where we were awarded again with best UI. What a great experience!
Thank you to Chris for his lovely writeup of the project, which the second paragraph of this writeup is based on.