Web apps with S3 + Rails. Now your apps have 2x as many buzz words.
developer.amazonwebservices.com
developer.amazonwebservices.com
Do any of the current online storage products do this already? I know some of the new ones use S3 (elephant drive and jungle disk, to name two), but I don't think either of them have a versioning feature built-in. It shouldn't be too hard to create...
http://niblets.wordpress.com/2007/02/16/how-i-set-up-my-ec2-instance-for-rails-litespeed/