I’m a vim user myself, and I was very happy to find that the guys at Akita On Rails had put together a small vim helper that allows you to jump directly to the APIdock page of the given Rails keyword. You can find it from their Github dotfiles commit.
Keep these contributions coming. :)
UPDATE: There’re now emacs bindings available as well.
UPDATE 2: One of our own guys also implemented a TextMate command.