The DC Animated Universe (DCAU) is a fan term for a series of popular animated television series and related spin-offs produced by Warner Bros. Animation which share the same continuity. Most of these series are adapted from DC Comics properties. This continuity is also sometimes referred to as the Timmverse (after producer Bruce Timm, the continuity's most consistent creative influence) and in the past, the Diniverse (after writer Paul Dini, who had mostly departed from Warner Bros. Animation when Justice League was in production).
Animated films and TV-series
-- https://en.wikipedia.org/wiki/List_of_television_series_based_on_DC_Comics --
DC Animated Movie Universe
The official Animated DC Universe ends with "The Zeta Project", but "Teen Titans" taking place after it is a decent continuity.
The four following "Batman" movies are a build-up to the "75th Batman Anniversary" movie with the same characters and voice actors of previous "Batmen" but are all stand-alone.
"Young Justice" would most likely take place prior to or during "Justice League [Unlimited]" as the story revolves around 'sidekicks' just as superheroes are becoming popular but inputting it in there in the already existing Animated DC Universe would break-up the timeline. Additionally, it takes place on a different earth in a different timeline/universe, so it can be thought of as a stand-alone. The same can be said of "Justice League Action" as it's a remake of "Justice League". "JLA: Trapped In Time", I'm assuming, would take place as a stand-alone or after "Justice League Action".
The following 22 movies/shorts/series are all stand-alone and sprinkled in to build on the lore of previous characters and their team-ups.
Finally, "Justice League: The Flashpoint Paradox" marks the end of the previous Animated DC
Universe jump-starting the canon DCAU based on "The New 52". Saving these for last would make a good conclusion to the stories and lore of the previous movies' characters and "Justice Leagues", and even to all the stand-alones, to start anew in the DC Animated Universe.
Lastly, I threw in "Ben 10" just for fun.