You mention Hanna Barbera, and their classic cartoons immediately come to mind: The Flintstones, The Jetsons, and Scooby Doo.
But how many remember Valley of the Dinosaurs, The Space Kidettes, Frankenstein Jr. and The Impossibles, Speed Buggy, and one of my all time personal favorites, Wait Til Your Father Gets Home?, which featured the voice talents of Tom Bosley right before he became Mr. Cunningham on Happy Days.
Warner Archives has been resurrecting many great lost movies you can buy to order, which means the studio pretty much personally burns you a DVD.
In addition to bringing back many films from the demands of fans, they’re also putting out long lost Hanna Barbera cartoons such as Funky Phantom, Dinosaurs, which closely resembles Land of the Lost with a modern family getting sucked back in time to prehistoric age, Jabberjaw, a goofy shark who’s a combination of Rodney Dangerfield and Curly of the Stooges, and more.
As for my personal favorites, I loved Jabberjaw as a kid, I vaguely remember Valley of the Dinosaurs and watching it today it’s a lot of fun, and Wait Til Your Father Gets Home, which was somewhat of a cartoon All in the Family. (The first season is available through Amazon.) Frankenstein Jr. and the Impossibles is also enormous fun, and I’m glad to see it finally officially available. (The Impossibles, a Beatles style rock group which had superpowers, also boasted some pretty cool tunes).
There’s also other Hanna Barbera compilations that have one or two episodes of their obscure cartoons put together by decade. In their 70’s compilations, you can get Inch High Private Eye, featuring a tiny little detective who can fit in a thimble, When In Rome, a situation comedy from the gladiator days (Hannah Barbara did a lot of Honeymooners style cartoons in different time frames, like in the stone age with the Flintstones, and in the future with the Jetsons), and The Chan Clan, with Charlie Chan’s family solving crimes.
Of course, for every Scooby Doo and Flintstones, there’s tons of Jabberjaws and Valley of the Dinosaurs. But again, if a cartoon fell in the forest, it doesn’t mean the fans didn’t hear it fall, and it’s great fun to go back and revisit the odd corners of cartoon history.