S3Stat is a log analysis tool for Amazon S3. This very helpful tool uses the log files generated by S3, analyzes them using Webalizer, and generates a variety of insightful and colorful reports. I have been using S3Stat on one of my own buckets for the last couple of months and have been pleased with the results. I use an S3 bucket to store the pictures that I post on my personal blog and now I know a lot more about the popularity of each one.
Take a look at the sample reports to learn more.
There's a one-month free trial and usage after that costs just $2 per month. Take a look at the pricing plan to learn more. While you are on the site you may want to take a look at their handy list of S3 resources as well.