From The Superman Homepage:
June 2006 is definitely the month for Superman. With the release of "Superman Returns", the annual Superman Festival in Metropolis Illinois and a whole slew of DVD releases. But if June is Superman Month, then June 20th is definitely "Superman Day", with 5 Superman related DVD sets being released on that day:
"The Adventures of Superman: Seasons 3 & 4", "Lois & Clark: The Complete Third Season", "Superman: The Animated Series - Volume 3", "Superboy: Season 1" and "Justice League: The Complete Second Season".