I just read this article and found it very interesting. I am a Product Manager at Quest Software and currently running a beta program for Capacity Management product. I would be interested to hear your feedback.
Capacity Management for SQL Server provides trend analysis of current disk use, forecasts of future disk space requirements, and notification when there is an immediate storage need.
To register for the beta program please visit http://www.quest.com/beta and click on Capacity Management for SQL Server 1.0