If you're looking for localizing you rails application, look here:
http://wiki.rubyonrails.org/rails/pages/InternationalizationComparison
But if you want a simple file with messages, you can use YAML...
-- my_strings.messages file (It must conform to YAML file format): error.msg.login.admin: You need to login before.... error.msg.field.required: This field is required,......
-- ruby code to load it require "yaml" messsage = File.open('my_strings.messages') { |yaml_file| YAML::load(yaml_file) }
-- and use it like a hash (It's a Hash indeed!) messsage['error.msg.login.admin']
HTH - H