DreamHost is one of the best (cheap 'n' realiable) Hosting for Rails. It offers a lot of services SSH, Mysql, Backup,... (like Site5) but the Rails support is better because you can choose among different technologies: Fcgi(deprecated), Passenger/mod_rails and Webrick(just for test), Mongrel.
Currently the gem installed is Rails 2.2.2, but you have a shell so you can choose (in Theory) whatever Rails version you like.
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