Heroku.com

Still one of most stable and mature PAAS solutions for ROR.

Scalingo.com

I haven’t used it but seems quite easy to use with their “Deploy to Scalingo” buttons (like here: https://github.com/covoiturage-libre/covoiturage-libre) and their own CLI tool to deploy applications.

Pricing: https://scalingo.com/pricing/osc-secnum-fr1

EngineYard.com

I also haven’t used this one but I have seen it pop up many times over years.

Pricing: https://www.engineyard.com/pricing/

Others

Few years ago I used OpenShift and I had good experience with it. I also tried using Azure Web Apps but that was hosted on Windows so it required JRuby and it was reaaally slow.

Sources

That's it for this post, thanks for reading!