Amazon S3 (Simple Storage Service) is a really interesting service. Well, at its core it's not terribly interesting at all - it just allows anybody to store data on Amazon's servers and access it at any time. A micropayment system lets Amazon offset the cost of providing the service. The interesting part is the low cost: Currently it costs $0.15 per gigabyte per month for storage and $0.20 per gigabyte of data transferred, with prices only expected to fall.
This kind of service is useful for backups or distributed computing or many other applications. Access control allows you (as the data submitter) to control who can access it. If you configure the service and your DNS correctly, you can even serve up content via the Amazon S3 servers over HTTP using your own domain name!
I was thinking about this and doing some back-of-the-envelope calculations. My web site currently contains 1.6 GB of content. Last month, my web site served about 8 GB of data. Let's run the numbers:
That's less than two dollars per month to host a reasonably busy web site. Of course, that doesn't give you any capability to host any dynamic content at all, but many types of web sites don't need that (including the vast majority of my own). You can enable logging for S3, so you can still extract the equivalent of HTTP server logs for the site.
At this time I'm not actually considering moving my web site from my hosted server to S3. There are too many other (non-HTTP-based) benefits of running my own server to give that up at this point, and if I'm running a server anyway, I might as well host my own HTTP server too.
You should expect to see an S3-based project or two from me in the near future.