I noticed an interesting feature on one of my university websites http://www.qmunity.org

The site allows you, somehow, to see how many people are viewing the site at the same time as you. It splits the users into 2 categories: ’Registered Users’ and ’Guests’

This has probably already been suggested but I thought if it wasn’t much hassle it might be fun. The moderators/programming team do a great job already though!
take it easy,oam