A cartoon -- excuse me, animated series airing on Kids' WB! at this writing. The show includes episodes of Superman: The Animated Series, The New Batman Adventures, and older Batman: The Animated Series (a/k/a The Adventures of Batman and Robin) episodes.
The cartoons are of good to excellent quality, with a slick style and voice acting well above, oh, say, Superfriends. No new episodes are being produced -- Kids' WB! has spent all the money it needs to make money on reruns.