Here is a list of the post-Crisis earths based on information from
spark...@mindspring.com (Steve Parker) and the
Infinate Atlas:
Earth-Sigma: The very short lived merged earth that existed Crisis #11 & 12, the few tie up loose end issues after Crisis, and the Legion of SuperHeroes until about 1989. If Superman or the LSH remembers Kara-El dying fighting the Anti-Monitor, Lady Quark comes from another reality rather than another planet, or people who are stated as dying during Crisis are alive at the end of issue #12 or issues immedately after then you are dealing with Earth-Sigma.
Earth-AC (Earth After-Crisis): Are Superman and a Kryptonian artifact called the Eradicator are the last survivors of Krypton which was a bleak sterile place? Is the Flash Wally West and taps into something called the Speed Force and there are dozens of other speedsters (including the original Flash with the Mercury-like bowl on his head) running around? Is Guy Gardner is running around with Sinestro's ring and Hal had a fake Green Lantern ring he was tricked into taking from some guy named Lord Malvolio (Action #632-#635) which may or may have not called him to go nuts and kill the GLC? Does the Justice Society originally never have a Superman, Batman or Wonder Woman as members? Is anytime Hawkman or the Legion of Superheroes is mentioned, people get headaches? Welcome to Earth-AC
Earth-ZH (Earth Zero Hour): The stillborn earth related on the back of Zero
Hour #0. Is there supposed to be only one timeline but Armageddon 2001 (which required alternate timeline to work) and the Supergirl of the Time Trapper's artificial alternate timeline still exist/happened? Is the current Hawkman a Native American? Does the JSA now have Wonder Woman's time traveling mother as a member? Do many time travel stories now make no sense what so ever? Welcome to Earth-ZH.
Earth-Hypertime (1999-current): Is Kingdom Come and every other Elsewords title part of the DU multiverse? Do the Superman titles have absolutely no continuity with each other or the rest of the DCU? Does Superman have both Matrix and a cousin called Kara-Zor-El who both answer to the name Supergirl? Does tying to make sense of about any character's history give you headaches? Welcome to the current mess known as Earth-Hypertime.