This answer included a clip of a deleted scene from Return of the Jedi. I has seen the deleted scene before, but I noticed this time that it included a brief shot of Vader sitting in his pressure sphere, which was almost certainly taken from footage that was originally shot for The Empire Strikes Back.
This set me wondering what other footage was reused. The other obvious example that immediately came to mind was the footage of the DEATH STAR firing controllers that was shot for A New Hope and appeared in Return of the Jedi. Compare the original sequence of firing on Alderaan:
with the sequence in Jedi (at 1:23).
(Similarly, the first poster for Revenge of the Jedi clearly shows a scene from Empire, with Luke and Vader battling in the Cloud City freezing chamber.)
So are there other examples of this reuse? As in the first case listed above, it's still interesting even if the reused footage did not make it into the final cut.
(My personal interest is primarily in the original versions of the first trilogy of films, but if there are example from other films in the series, feel free to post them. It would also not be surprising if footage were reused in lower-budget television programs, like the Star Wars Holiday Special or The Ewok Adventure. As noted in the comments, the Holiday Special has lots of obvious footage from A New Hope, particularly of Han and Chewie in the Millennium Falcon cockpit.)