The Drive Space Event Monitor checks the attributes of specified disk drives on remote machines. This video, among other things, will teach you how to configure notifications if the amount of available space changes by more than a certain size or percentage. It's a great way to get notified when someone dumps a large number of files on a server.
To learn more about the features of the Drive Space Event Monitor, watch this video or access the text-based tutorial here. To view this video on YouTube, click here.