[eluser]Aken[/eluser]
Sometimes controllers can be huge. It depends on what's going on throughout. You'd have to share it with us if you want specifics for your situation (use an online service such as Pastie or Github Gists).
Helpers and libraries are appropriate if you plan on using that particular code in more than one place. If you find yourself repeating code, these are certainly options.
Another solution to keeping things DRY is to use private/protected methods in the controller. That's a good way to separate things, also, if you really want to break apart a single method.
