I've inherited some old Maxwell House haggadot, from the 1980s. They're in perfect condition, but we simply prefer more modern styled ones now. What would be a proper and respectful way of getting rid of them? Some very nice, creative haggadot have come around in recent years that I'm very fond of, and at this point, I prefer these over the old standards.
Since Hagadas have complete Pesukim they are considered a sacred object. Thus the correct way to dispose of them is to place them in Geniza. Here is a link explaining Geniza.