Sinatra-S3-Direct-Upload is a project mainly written in JAVASCRIPT and RUBY, it's free.
Direct Upload to Amazon S3 with jQuery SWFObject and Sinatra
A simple Sinatra app to upload files directly to Amazon S3 using jQuery SWFUpload.
Tested on ruby 1.9.2. Install these gems if you haven't already:
gem install activesupport
gem install hpricot
gem install sinatra Make sure hpricot is at least at version 0.8.3
Put the crossdomain.xml file in the root of your s3 bucket and make it readable.
Modify the bucket, access_key, and secret_access_key variables at the top of main.rb to match your AWS credentials.
$ruby main.rb Then go to http://localhost:4567/upload