I would say EL Passion is one of the finest Agile Ruby on Rails development companies in Europe.
Check out their work, and especially the design. They really create beautiful web apps.
At Panzertechnologies.com is a Right Company for Ruby on Rails Application Development Services in USA, India. It is passionate about Rails and our dedicated ROR Developers can create web 2.0 applications using latest Ruby on Rails web services. Call once (203) 652-7866.
Panzer Technologies is a leading Ruby on Rails Development company in India. Panzer Tech has developed large application in past, so I think they can handle large projects. You can visit there website www.panzertechnologies.com