How crazy are the Maenads from Greek Mythology? I have read about the Maenads, how they were insane followers of the god Dionysus, that their names literally meant "the raving ones" and that they were frequently in a state of ecstatic intoxication. Are there any tales about them doing activities that are exceptionally insane and what lead to the Maenads being such crazy followers of the god of wine and parties?

They weren't just insane followers, they were supposedly nurses too. They were mad because of alcohols and drugs, and showed the "dark" side of the party. Sometimes, drinking too much cause violence, sometimes violence cause death. "Real" followers of Dyonisos tried to emulate their madness with mushrooms and other psychotropes. For some reason, this is cited in the french wiki article but not in the english one (aforementioned french menead article)

About their most crazy acts in myths, they're very rare actually. Some greek hero had to chase them and they moved weirdly, bending unnaturaly etc, but I sadly doubt any tales is centered about them. The wikipedia articles are kinda well documented, this could be a good start even though it's not perfect