combining controller actions

Though I'm very new to Rails, I've been chugging along with the
tutorials that are available. They're quite fun. While building my own
web apps, I've decided to use a different URL scheme than the default
controller/action/id scheme Rails defaults to.

For instance, I'm working on cloning a small section of YubNub, where
URLs like http://yubnub.org/parser/parse?command=gim+dogs redirects
the user to a Google Images query for dogs. When most of the activity
will take place in one action (parse), there doesn't seem to be a good
way for Rails to delegate actions. Because there is no real route for
Rails to follow to get to the many actions (command=google,
command=yahoo, command=ask), I can't just tell the various methods to
render or redirect_to those actions. Also, any HTML forms I have in
place cannot access an action unless there is a route to it. This
makes sense--how else would the browser know which URL to send the
form information?

Another example would be creating a wiki, where the default action
should be to show a wiki page, but routing overrides any request to do
things like http://site.com/wiki/SomePage?action=edit or
http://site.com/wiki/SomePage?action=delete.

Currently, I've been cutting and pasting the code from action methods
such as show, edit, destroy, and so on into one really big index
method. I know this is slipping into spaghetti code territory, so I
want to know if there is a better way of doing this.

Initial code as routed for controller/action/id URL scheme
http://site.com/parser/command.

def index
  respond_to { |format| format.html }
end

def google
  respond_to { |format| format.html }
end

def yahoo
  respond_to { |format| format.html }
end

def ask
  respond_to { |format| format.html }
end

Code after combining into single action for use with URL scheme
http://site.com/?command=<service>.

def index
  case params[:command]
    when "google"
      respond_to { |format| format.html } # google stuff...
    when "yahoo"
      respond_to { |format| format.html } # yahoo stuff ...
    when "ask"
      respond_to { |format| format.html| # ask stuff ...
  end
end