I wish calendars would come with booking ability. If I want to schedule a conference room, a laptop, the company car, and the spare parking permit (for example), I have to go to four separate calendars. I'd rather be able to schedule an event and assign resources to it.
I've used Rapla (http://rapla.org/) for this in my lab, and it worked nicely. You schedule an event, it lets you know what resources are available for that timeslot.