Over the last week or so, I’ve had the opportunity to work with the reports available in Quest’s Site Administrator for SharePoint toolset. The out of the box reports that it provides can help you greatly in administering your farm. See this PDF document for a list of all of the out of the box reports.
Since it’s built on Reporting Services, you can also create what ever custom reports you might need. For instance, in just a few minutes we created a report that showed us the Site Administrators for every Site Collection in the farm.
There’s a freeware version you can take a look at to see some of what it can do, and also a trial version, both available at the above link.