I was in college when i discovered Batman: The Animated Series back in '92 and I immediately loved it. I had really liked the two Tim Burton Batman films, especially due to Danny Elfman's scores, but I had never read a Batman comic previously. BTAS was and is an amazing show in all aspects, whether its character design, voice talent, art direction, music, writing, direction, sound design, etc etc. With the recent 4-disc release of music from the show, I was revisiting a number of episodes in the DVD sets.
I never wound up seeing Batman Beyond, STAS or JL/JLU, the latter only recently. I purchased the complete JL/JLU series on DVD last year, found it at Amoeba Records here in L.A. for a great price, and I really enjoyed diving back into the DCAU, especially for Batman's continuing arc. I picked up season one of BB as well.
This also led me to seek out the comic book series from the 90's set specifically in the animated universe, such as the aforementioned "Lost Years". And then I finally started to dive into the larger world of Batman comics, starting with the various collections like "Batman in the 70's", "Birth of the Demon" and "The Greatest Batman Stories Ever Told". It's been a real treat to discover these marvelous comics, especially the work of Denny O'Neil. I keep finding items in the comics that found their way into BTAS!