You could use sparklines or something like that, but instead I'd recommend presenting your data overlaid on top of a table of people's names, or perhaps a seating chart to add the additional information of where they are.
Assuming you just need to visualize whether or not someone is busy now, you could fill the box surrounding each name with a solid color on a scale depicting how busy they are. If someone is available: green or white. If someone is busy: red. You could use yellow as an intermediate color if you want. This way someone could look at the board and immediately know who's busy and who's not.
You could add a time component to this visualization technique as well: divide the box containing a person's name into six (or fewer/more) sequential segments. Color each segment in accordance to how busy they were during a particular time period, such that the current time is the rightmost box and how busy they were an hour ago is the leftmost box.
Activity over last hour (or whatever period you want, really):
If you use this alternate technique, you may want to exaggerate the "now" box somehow, perhaps making it larger than the others or darkening the color of the historical boxes to make the "now" box brighter. This would have the added effect of probably making people look like they were historically busier than they actually were, so you probably don't want to go that route: I'm just providing you with ideas you can work with.
These are just some rough mockups I threw together in excel to demonstrate my idea. I'm sure you could make this look much better: I'd suggest adding some padding between each box. Also, you don't really need a border around each name. But I"ll leave these design considerations up to you.
UPDATE: Regarding your history page, something else you could have would be an aggregate trends page (since this is clearly something you are interested in) where you visualize each persons busyness by each day of the week, perhaps since the beginning of the semester or over the last two weeks. So each person in the department would get a separate graph like this (showing which days and at what times they are busy:
Image via: http://unsupervisedlearning.wordpress.com/2012/09/26/who-is-rwashingtondc-part-1-daily-activity-usage/