I recently receive this bill from Amazon for my S3 locker.
This e-mail confirms that your latest billing statement is available on the AWS web site. Your account will be charged the following: Subtotal: $0.02 (plus applicable taxes)For those of you who haven't taken notice yet - you can basically buy disk space "in the sky" as it were very cheaply from Amazon. Pay only for what you use (as you can see, I haven't used much yet).
I'm still figuring out what I might want to use this for - I was thinking about possibly an off-site backup for digital photos. With a bit of effort, you can access them from anywhere with net access and never need to track down those files again.
For music, though, it's cheaper to use the Oboe Locker from MP3Tunes... for $40 per year, you get unlimited disk space, as long as you're only storing music files.
If you've never played with virtual disks that are always available, you are in for a treat. Of course, it's really geared more towards technical people at the moment, but this is the future we're looking at...