jclouds provides any-weight clouds tools for Java 5 and later: you choose the depth you want. We are pleased to announce our first beta of jclouds-s3. jclouds-s3 provides both Map<String,InputStream> and FutureCommand interfaces to Amazon S3.
It features a pluggable core, most notably supporting Apache HttpNio and Google App Engine for Java runtimes.
Please have a look at our project page and give it a try. We welcome your feedback and participation.