Sources for the film: references

Well, a big reference you didn't mention was "The Trip" for the LSD scene-complete with non-computer enhanced visual tricks, similar to what they used in the 60's to film those movies. Other references:

"Valley of the Dolls", when Edith asks Angela how many dolls she took, because Angela's really out of it.

"Dead Ringer"- The other Bette Davis twin movie, but in this one, one twin deliberately kills the other and assumes her life.

The "For me!" speech wasn't so much "Gypsy", but more a tribute to those rants that Bette Davis would do in her films.

"Where did it all go wrong?" was a play on Susan Hayward and her Brooklyn accent.

The character of Barbara Arden was a take on Joan Crawford in such films as "Mildred Pierce" and "I Saw What You Did", the really sweet as pie Joan, not Joan the destroyer.

The death of the housekeeper was reminiscent of "Whatever Happened to Aunt Alice?"

The look of the dinner scene that precedes the LSD scene was stolen directly from "Hush Hush...Sweet Charlotte".

The fact that Edith steals her mother's lover is right out of "Mildred Pierce"

The Jason Priestly character that seduces Angela, Lance and Edith was similar to Michael York in "Something for Everyone".

I think the Bette Davis vehicle DEAD RINGER (DR) was the most influential film on DMD. Consider:

1. The obvious similarity is that both films have identical twins as principal characters, with one murdering the other and the surviving twin assuming the identity of the deceased. In both films, the surviving twin is found out towards the end. Also, in both films the nice twin murders the nasty twin.
2. Both films have characters named "Edith" and "Tony." Significantly, Tony Parker in DMD is a gigolo to Angela while Tony Collins in DR is a gigolo to the main character.
3. Angela's son mentions that the funeral reception was at the home of Peter Lawford's agent. Peter Lawford was in DR.
4. Charles Busch often times comes close to impersonating famous actresses in DMD. But, I only noticed one instance where he blatantly impersonates: the scene where Angela throws Tony Parker out of the house, saying "Get out....GET OUT." This is directly out of DR when Bette is throwing Tony Collins (Peter Lawford) out (just prior to the dog attack). Angela recites the same lines precisely the way Bette did in DR, including gestures. This had to have been deliberate on Busch's part.
5. The ending of DMD is straight out of DR. After Bette's last line in DR, she gets into a police car and is then driven away. Same exact ending for DMD.

DMD owes more to DR than any other film in my opinion. Busch is very well acquainted with DR since he provides commentary on the DVD.

I adore DMD and wish Busch would give us more, more, more.

I'm surprised no one has mentioned the Lana Turner vehicle "The Big Cube"- that's the inspiration for the LSD flashback, as Lana's bitch of a stepdaughter slips her the damn cube as revenge for her father's death!