Tales of the Wizard of Oz. As cheap as the animation may be, it's a clever, witty, aesthetically pleasing 60s cartoon series, and perhaps one of my favorite Oz adaptations that isn't the MGM movie.
On a similar note, there's also their TV special Return To Oz (which was released the same year as Rudolph the Red Nosed Reindeer) which has marginally better animation, still a bit off kilter, but still corny and fun as well, despite the fact that it's just a re-hash of the plot of the MGM movie. (I believe Arthur Rankin Jr. or Jules Bass admitted to it being essentially an animated version of the 1939 Oz movie in one interview.)
I'm surprised nobody's yet brought up the crowdfunding campaign going on for a
Rankin/Bass documentary made in cooperation with historian Rick Goldschmidt (who also runs
a wonderful blog filled with 60s animation art and assorted TV memorabilia) which would be exciting to see if it comes through...
I could go on all day with the other Rankin/Bass classics...