s3inabox is a Vagrant appliance that can be used to fire up a VirtualBox virtual machine containing an embedded version of Amazon S3 provided by boardwalk.
All of the boardwalk limitations exist. It's currently only been tested using the right_aws gem to access the API.
It's also currently in a half-working state because I haven't finished tweaking the chef configuration.
All included cookbooks are licensed under the specific terms included in their README. All other files are licensed under the Apache 2.0 license.