I\'m looking to add functionality to my Rails app to upload files directly to Amazon S3. From my research the general consensus seems to be to use the s3-swf-upload-plugin.
Try looking into carrierwave https://github.com/jnicklas/carrierwave (supports s3)
Multi file uploads with carrierwave and uploadify http://blog.assimov.net/post/4306595758/multi-file-upload-with-uploadify-and-carrierwave-on