Amazon S3 storage doesn't appear to have a built-in reporting feature for getting resource usage statistics. Fortunately, there's s3stat.com which seems to do this in a breeze.
The site has a .NET desktop application which automates the (somewhat painstaking) task of setting up a dedicated Amazon IAM user account and enable reporting on the bucket of choice.
Once the 30-day trial is up, the service starts at $10 USD/month.
I'm starting my free trial now to get some real-world analytics out of my Amazon S3 hosting.
If you know of any other services that offer something similar, please leave it in the comments below.