Announced today, Amazon S3 is a giant hard drive with only an API. There is no "Windows Explorer" way of using it (yet). Websites all over the Internet, like ours, could use Amazon's hard drive to store our images and other media files and take advantage of their huge infrastructure and support staff with just a few lines of code.
We have been looking to add file storage to let our customers upload files for their participants (rather than wait for a webmaster to upload to their own site). We have been hesitant to take on managing the storage and versioning of these files. But, at $0.15 per gigabyte of storage and $0.20 per gigabyte of transfer, I think we're running out of excuses!