map.connect ':controller/:action/:user_name'

@params = {:controller => "profile", :action=> "view", :user_name => "john"}

map.connect ':controller/:action/:user_name',
   :requirements => {:user_name => /w+/}

class User < ActiveRecord::Base
  def to_param
    "#{id}-#{name.gsub(/W/, '-').downcase}"
  end
end

map.resources :users