I lucked upon a way to play Hulu Plus from my iPad to my Apple TV. I can launch Flixster, start watching a trailer, hit the Home button, launch Hulu Plus and pick a show to watch and it plays on my Apple TV. This didn't work trying my Videos app first. So far it only works by launching Flixster, watching a trailer, then going to Hulu Plus. Seems to stay connected until I completely close Flixster or Hulu Plus.
Finally, a way to watch Hulu Plus on my Apple TV.
Both Apple TV and iPad are running iOS 4.3.