S3auth.com; a Free Http Auth Gateway In Front Of Amazon S3 Bucket
We sponsored a small hosted service for owners of Amazon S3 buckets: s3auth.com. Amazon S3 doesn't provide an ability to deliver private content through HTTP Basic/Digest authentication mechanisms. Our hosted service fills this gap.
The product already received good feedback from users worldwide. What is especially interesting is that the web service is a fully open source and is hosted at github. The service itself, of course, is hosted at Amazon EC2.