I've written previously about my frustration with reporting in PowerShell - how I see admins struggle with ugly, low-level COM code to manipulate Excel spreadsheets, just so they can get nice-looking reports with a degree of automation.
The right thing to do is put your data in SQL Server, and use SQL Server Reporting Services to generate awesome looking reports, complete with charts and graphs. With the right setup, you can completely automate data collection, report generation, and delivery. And it doesn't have to cost a single dime. Plus, the learning curve isn't too steep, and the skills you'll learn along the way will be massively beneficial to you over the long haul - far more so than the time sunk into becoming an Excel jockey.
So I've written a little book about it, which you'll find on at https://powershell.org/ebooks, entitled Making Historical and Trend Reports in PowerShell. Unlike my earlier book on HTML reporting, which was mainly around producing inventory reports, this one's specifically designed to make reports based on collected-over-time data, like disk utilization, performance, and so on. And I've bundled in a PowerShell module that should make this easy, insulating you from 99% of the SQL Server-related stuff.
Right now (November 2012) I'm looking for folks to test stuff out and let me know (via comments here) if you find any problems. I want to make sure that what I've got in here works and is understandable. Final publication is scheduled for January 2013, after which I'll start taking suggestions for stuff to add to the book.