They're on the Cartoon Network and its spinoff, Boomerang, the latter which specializes in 60s and 70s cartoons. They show most of the classic Hannah-Barbera stuff and a lot of the more obscure ones as well, along with related non-HB stuff like Bullwinckle Banana Splits. The ones I watch most are Scooby Doo, Superfriends, and the 1960s predecessors to Superfriends. I also like Fractured Fairy Tales, which is hilarious :)