WIth the new iMac how do we connect an external screen?
Thunderbolt is a superset of Displayport Apple page on Thunderbolt says


  And because Thunderbolt is based on
  DisplayPort technology, the video
  standard for high-resolution displays,
  any Mini DisplayPort display plugs
  right into the Thunderbolt port. To
  connect a DisplayPort, DVI, HDMI, or
  VGA display, just use an existing
  adapter.