I am frequently asked how reliable/scalable is Ruby on Rails? I usually tell people about Twitteror more recently point them to this article about the Friend’s For Sale Facebook application. The answer is, yes Rails scales just fine. The trick is getting your database to scale.
Here are two of the places to look for the big Rails deployments:
The elegant, framework that lets developers enjoy their job once again is scalable and will work for you application. I love Ruby on Rails.