I'm ding some processing on business data using EMR and my output is saved in S3. I have to setup a confirming dashboard to come to light up this processed data. I had been considering various options and appears Ruby on Rails is nice framework to begin with.

Can you really hook data from S3 to RoR driven website? If so, how ?

Any pointer could be useful. Do tell me if you will find every other free platform that we may use.

What you'll most likely be thinking about, is applying Paperclip (or any other similar jewel) to keep the information on S3. In your application, after that you can locate/compute the information you will need to display using your Paperclip-based model, then have Paperclip retrieve and load the information you'll need.

The excellent factor about this type of option would be it's completely transparent for you personally (like a user So that as a developer): you are just dealing with your objects, plus they get saved/retrieved form S3 when needed.

Both Heroku and Engineyard (most likely the 2 biggest cloud companies for rails) use S3 because the after sales, so with such companies might be great.

Heroku is commonly more 'out-of-the-box' and so i think EngineYard with CLI(Command Line) access could be more appropriate for your needs.

More information around the two at
Heroku vs EngineYard: which one is more worth the money? and
http://mikemainguy.blogspot.com/2011/08/heroku-is-bus-engineyard-is-car.html and
http://www.cuberick.com/2010/04/engine-yard-vs-heroku-getting-started.html has more about setup / cost.

This is possible. Make use of the fog jewel.

I must not recommend you utilize carrierwave or paperclip for the specific needs here. They are good when you're uploading the information initially, however in your situation you are being able to access existing data. Only use fog for connecting to s3 directly.