Yes, it does have a tiny bit of a cost. But if you're at risk of going over your webserver's quota for space or bandwidth, Amazon's S3 is a great alternative for the cheap fix that kicks in as needed. What I didn't realize is that the Amazon data is URL addressable: Coding Horror: Using Amazon S3 as an Image Hosting Service.

That's fantastic.

Not that I have anything huge to put up in the short-term, but it's nice to know (since like so many people I'm an Amazon customer and a geek with all sorts of extra Amazon services) I have a place I could quickly upload large data, let it be accessible, and then remove it, and throw Amazon some well deserved coin.